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Dr. Venkataiah Gorige

  • Assistant Professor
  • School of Physics
  • University of Hyderabad

About Venkataiah Gorige

Dr. Gorige joined the School of Physics, University of Hyderabad in December 2013 and his research oriented towards Magnetic Materials & Multiferroics. Particularly, manipulation of magnetism in Ferromagnetic/Ferroelectric heterostructured thin films and bulk composites by thermal and electrical means via magnetoelastic coupling without using any electric currents and realizing device applications at ultra-low energy consumption.

After receiving PhD degree from Osmania University, Hyderabad in 2007, he was a Postdoctoral Fellow at Department of Physics, National Cheng Kung University, Taiwan for about two and half years. Subsequently, he was awarded JSPS Postdoctoral Fellowship for FY 2010, by the Japan Society for the Promotion of Science to work in Japan. Therefore, in connection with JSPS Postdoctoral Fellowship, he moved to the Laboratory for Materials and Structures, Institute of Innovative Research, Tokyo Institute of Technology, Tokyo and worked with Prof. Tomoyasu Taniyama for a period of two years. After returning from Japan, he was a CSIR Senior Research Associate at Department of Physics, Indian Institute of Science, Bangalore and he was working with Prof. P. S. Anil Kumar before joining the School of Physics, University of Hyderabad.

Academic Positions

  • Present 2013

    Assistant Professor

    University of Hyderabad, School of Physics

  • 2013 2013

    Senior Research Associate (CSIR)

    Indian Institute of Science, Bangalore, India. Department of Physics

  • 2012 2010

    JSPS Postdoctoral Fellow

    Tokyo Institute of Technology, Japan. Materials and Structures Laboratory

  • 2010 2008

    Postdoctoral Fellow

    National Cheng Kung University, Taiwan. Department of Physics

Education & Training

  • Ph.D. 2007

    Ph.D. in Exp. Condensed Matter Physics

    Osmania University, Hyderabad, India.

  • MSc 2002

    Solid State Physics

    Osmania University, Hyderabad, India.

  • BSc2000

    Mathematics, Physics, and Chemistry

    Osmania University, Hyderabad, India

Honors, Awards and Grants

  • 2017
    Associate Fellow
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    Telangana Academy of Sciences, Telangana, India
  • 2017
    Best Poster Award
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    ICMAGMA-2017 at Defence Metallurgical Research Laboratory, India
  • 2013
    Best Poster Award
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    IUMRS-ICA at Indian Institute of Science, India
  • 2013
    Senior Research Associateship
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    Council of Scientific and Industrial Research, India
  • 2010 - 2012
    JSPS Postdoctoral Fellowship
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    Japanese Society for the Promotion of Science, Japan
  • 2008-2010
    Post-doctoral Fellowship
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    National Cheng Kung University, Taiwan
  • 2008
    Awarded Research Associate
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    Council of Scientific and Industrial Research, India
  • 2007
    Awarded Young Scientist
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    Dr K V Rao Scientific Society, Hyderabad, India
  • 2006-2008
    Senior Research Fellowship
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    Council of Scientific and Industrial Research, India.

Research Summary

Overview

  • Multiferroic Materials that exhibit two or more ferroic orders, such as magnetic (ferromagnetic, anti-ferromagnetic or ferrimagnetic); ferroelectric; ferroelastic or ferrotoroidic.
  • Magneto-electric (ME) effect is the production of electric polarization with the application of magnetic field or conversely magnetization with electric field.
  • The materials needs to break space inversion symmetry and time reversal symmetry to exhibit ferro-electricity and ferromagnetism, respectively. In order to realize linear ME coupling in a material, space inversion and time reversal symmetries are to be broken, while for strain mediated ME coupling no symmetry constraints are imposed and this can be easily achieved in FM/FE heterostructures and composites.
  • The strain induced ME effect in FM/FE heterostructures is 30 000 times bigger that linear ME effect in single phase materials.
  • Therefore, FM/FE heterostructures and composites are best suitable candidates to realize strain mediated ME coupling and explore these materials for possible device applications.

Objective

  • Manipulation of magnetism in magnetic/FE heterostructures and composites by thermal and electrical means via magnetoelastic coupling without using any electric currents and to realize the device applications at ultra-low energy consumption.

Materials

  • Multiferroics of magnetic/ferroelectric heterostructures (thin films)
  • Particulate composites (bulk)

Methodology

  • Materials preparation: Sol-Gel technique (bulk) & PLD (thin films)
  • Characterization techniques: XRD, SEM, TEM etc.
  • Physical properties: Magnetization, Resistivity, Magnetoelectric, Dielectric and Magneto-Optical Kerr Effect etc.

Interests

  • Magnetic Materials & Multiferroics
  • Ferromagnetic/Ferroelectric Heterostructures
  • Electric field Control of Magnetism
Multiferroic Magnetoelectric PLD MOKE

Previous Results

  1. Strain induced magnetic anisotropy

    Strain induced M_1
    Strain induced M_2

  2. Strain induced magnetization switching

    Strain induced M switcing

  3. Electric field induced magnetic coercivity

    Electric field_1
    Electric field_2

Research Projects (in progress)

  • Interfacial multiferroic magnons: understanding of cross-corelation towards magnonic logic circuit applications; Indo-Japan (DST-JSPS) Collaborative Joint Research Projects, 2019-2021.
  • Spin wave dynamics in ferromagnetic/ferroelectric heterostructures; SERB CORE Research Grant, 2020-2023.

Research Projects (Completed)

  • Strain mediated magnetoelectric coupling in ferromagnetic/ferroelectric multiferroics, UGC, Govt. of India, 2015-2017.
  • Electric field control of magnetoresistance in TMR/ferroelectric heterostructures, Laboratory for Materials and Structures, Tokyo Institute of Technology, Japan, Collaborative Research Projects–2015 & 2016.
  • Manipulation of magnetism in ferromagnetic/ferroelectric multiferroics, SERB, Govt. of India 2015-2018.
  • Electric-field control of magnetism in La1-xSrxMnO3/BaTiO3 heterostructures; CSIR, Govt. of India, 2016-2019.

Collaborations

  • Prof. Taniyama Tomoyasu, Department of Physics, Nagoya University, Japan.
  • Prof. P. S. Anil Kumar, Department of Physics, Indian Institute of Science, Bangalore, India.

Laboratory Personel

PhD Students

Avisek Das

PhD Student [D5]

Registration Date & No.: 20.08.2015 [15PHPH19]

BBL Fellowship, UoH

Praneetha B

PhD Student [D5]

Date of registration: 30.07.2015 [15PHPH02]

Junior Research Fellowship, CSIR, India

Sridhar Aeggidi

PhD Student [D1]

Date of registration: 03.01.2020 [19PHPH20]

Junior Research Fellowship, CSIR, India

Mrinalini

PhD Student [D1]

Date of registration: 06.11.2020 [20PHPH03]

BBL Fellowship, UoH

Rajesh Kumar

PhD Student [D1]

Date of registration: 06.11.2020 [20PHPH08]

BBL Fellowship, UoH

Postgraduate Students

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Mr. Nitin Yadav

MSc-Physics-III

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Mr. Bonala Sreenivasulu

IMSc-Physics-III

Alumni (PhD)

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Dr. Anupama Swain

Awarded, August 2019

Thesis Title: Charge Order Supression and Magnetization Switching in Manganites

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Mr. Prakash Bongurala

Submitted, November 2020

Thesis Title: Structural, magnetic and dielectric properties of NiFe2O4-BaTiO3 magnetoelectric multiferroic composites

Alumni (Master Students)

Mr. Kranthi Kumar B, MSc, 2020

Mr. Praneeth, MSc, 2019

Mr. Altaf Hussain, MSc, 2018

Mr. Rajesh Puntia, MSc, 2017

Mr. Bikash Sahoo, MSc, 2017

Mr. Mangababu, MSc, 2016

Mr. Abhinav, MSc, 2015

Mr. Kumar Rathod, MSc, 2015

Former Visiting Students

Mr. John Abraham; IISER Thiruvanathapuram

Ms. Yogita Taneja; Central University Karnataka

Publications

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(37) Influence of cation distribution on magnetic response of polycrystalline Co1-xNixFe2O4 (0 < x < 1)ferrites

K. K. Bestha, J. J. Abraham, J. A. Chelvane and V. Gorige *
Journal Articles Physica Scripta 95, 085802 (2020)

The present paper reports the interconnection between cation distribution and physical properties of Co1-xNixFe2O4 (0 ≤ x ≤ 1) samples to tune them for suitable applications at room temperature. A set of five Co1-xNixFe2O4 (CNFO) samples with different nickel concentration (x) were prepared by using citrate-based 'sol-gel' method. The x-ray diffraction (XRD), Raman spectroscopic and scanning electron microscopic techniques were employed to characterize the samples structurally and morphologically. The Rietveld refinement of diffraction data confirms the monophasic spinel cubic structure with space group. The cationic arrangement between the tetrahedral (A-) and octahedral (B-)sites of (AB2O4-type) CNFO samples was estimated from the diffraction intensities of XRD and the spectral peaks of Raman data. Based on the cation arrangement, the estimated magnetic moment values, by adopting Neel's sublattice model, were in correlation with each other and found to reduce with the rise in nickel content. A systematic change in the lattice, spectral and magnetic parameters with an increase in nickel content in CNFO, clearly ensures the transformation from hard to soft magnetic behavior of the samples. The marked magnetic transformation was elucidated in the framework of cation distribution. The tuning of magnetic parameters and cation distribution in ferrites with an appropriate element substitution might be a viable approach to make them for desired high-frequency magnetic applications.

(36) Correlation between size, shape and magnetic anisotropy of CoFe2O4 ferrite nanoparticles

A. Das, K. K. Bestha, P. Bongurala and V. Gorige *
Journal Articles Nanotechnology 31, 335716 (2020).

The present work reports the effect of particle size and shape of CoFe2O4 (CFO) nanoparticles on magnetic properties and their use in device applications as permanent magnets at room temperature. A set of CFO samples with different particle sizes and shapes were synthesized via the polymeric method by sintering at temperatures ranging from 300 ◦C to 1200 ◦C. These materials were characterized structurally by x-ray diffraction, morphologically by scanning electron microscopy, and microstructurally by transmission electron microscopy. The morphology of these CFO samples shows size-dependent shapes like spherical, pyramidal, lamellar, octahedral and truncated octahedral shapes for the particle sizes ranging from 7 to 780 nm with increasing sintering temperature. The emergence of magnetic properties was investigated as a function of particle size and shape with a special emphasis on permanent magnet applications at low and room temperatures. The values of saturation and remnant magnetization were found to increase monotonously with a particle size up to 40 nm and from thereafter they were found to remain almost constant. The other magnetic parameters such as coercivity, squareness ratio, anisotropy constant and maximum energy product (BHmax) were observed to increase up to 40 nm and then decreased thereafter as a function of particle size. The underlying mechanism responsible for the observed behavior of the magnetic parameters as a function of particle size was discussed in the light of coherent rotation, domain wall motion and shape induced demagnetization effects. The significant values of BHmax - the figure of merit of permanent magnets - observed for single domain particles (particularly, 14 nm and 21 nm) were found to have suitability in permanent magnetic technology

(35) Electrical conduction mechanism for the investigation of charge ordering in Pr0.5Ca0.5MnO3 manganite system

A. Swain and V. Gorige *
Journal Articles J. Magn. Magn. Mater. 485, 358 (2019)

In the present work, a systematic investigation of electrical transport mechanism has been used as a tool to investigate the charge-order suppression and its crossover in Pr0.5Ca0.5MnO3(PCMO) manganite system with varying particle size and applied magnetic field. The samples with different particle sizes were synthesized by adopting sol-gel method and sintering at different temperatures. The prepared samples were thoroughly characterized by various physicochemical techniques. The activation energy and density of states at Fermi level obtained from the temperature-dependent electrical resistivity data clearly show the charge order crossover signatures and its suppression in the samples below 70 nm particle size and applied magnetic fields above 4 T. The significant change in various electrical transport parameters with the particle size around 70 nm could be attributed to the melting of long-range charge ordering behavior due to surface spin disorder and induced lattice-strain effects in PCMO manganite system.

(34) Irreversible meta-magnetic transition in charge ordered Nd0.5Ca0.5MnO3 manganite

A. Swain and V. Gorige *
Journal Articles Phys. Status Solidi B: Basic Solid State Physics 485, 358 (2019)

The investigation of charge ordering (CO) suppression and consequence effects in manganites are of interest to the scientific community as they help them to understand the interactions among the spin, charge and orbital degrees of freedom of conduction electrons. In this work, the suppression of CO in small bandwidth half-doped manganite, Nd0.5Ca0.5MnO3 (NCMO) has been demonstrated by reducing the particle size. Bulk and nano forms of NCMO materials were prepared by sol-gel technique and characterized by various physicochemical techniques. The magnetic and magnetotransport properties of bulk samples show the exciting features, viz., CO, training and irreversible metamagnetic effects, whereas these features are significantly suppressed in the nanoscale sample. The observed behavior in the present investigation was explained in terms of magnetic phase separation and spin memory effects. Our investigation establishes a combined effect of surface spin disorder and lattice strains for the suppression of CO behavior in NCMO manganite system.

(33) Structural, magnetic and electric properties of multiferroic NiFe2O4-BaTiO3 composites

P. Bongurala and V. Gorige *
Journal Articles J. Magn. Magn. Mater. 477, 350 (2019)

The room-temperature magnetoelastic coupling has been demonstrated in (x)NiFe2O4+(1-x)BaTiO3 (where x = 0-1 with a difference of 0.1) composite system by investigating its structural, magnetic and ferroelectric properties. The samples were prepared by a standard solid-state reaction method and characterized by x-ray diffraction, backscattered scanning electron microscopy and energy dispersive x-ray spectroscopy techniques. The temperature dependent magnetization data clearly show the significant jumps in magnetization curves at structural phase transitions of BaTiO3, signifying the strain-mediated converse magnetoelectric (CME) coupling in NiFe2O4-BaTiO3 multiferroic system. The substantial changes observed in the values of obtained parameters from structural, magnetic and ferroelectric properties clearly ensuring the strain-mediated magnetoelectric (ME) as well as CME effects in this system. The present investigation indicates that the NiFe2O4-BaTiO3 composite system will be a potential candidate for the future low-power consumption device applications at room temperature.

(32) Strain-mediated magnetic response in La0.67Sr0.33MnO3/SrTiO3/La0.67Sr0.33MnO3/BaTiO3 structure

A. Swain, K. Komatsu, M. Itoh, T. Taniyama, and V. Gorige *
Journal Articles AIP Advances 8, 055808 (2018)

Electric field controlled magnetism is an exciting area of condensed matter physics to explore the device applications at ultra-low power consumption compared to the conventional current controlled or magnetic field controlled devices. In this study, an attempt was made to demonstrate electric field controlled magnetoresistance (MR) in a tri-layer structure consisting of La0.67Sr0.33MnO3 (LSMO) (40 nm)/SrTiO3 (10 nm)/LSMO (10 nm) grown on a 500-μm-thick BaTiO3 (001) (BTO) single crystal substrate by pulsed laser deposition technique. Epitaxial growth of the trilayer structure was confirmed by x-ray diffraction measurements. Jumps observed in the temperature-dependent magnetization curve at around the structural phase transitions of BTO ensure the strain-mediated magnetoelectric coupling between LSMO and BTO layers. A significant change in MR of this structure in applied electric fields does not show any polarity dependence. The findings are related to the lattice strain-mediated magnetoelectric coupling in ferromagnetic LSMO/ferroelectric BTO heterostructures.

(31) Magnetization Reversal in Fe/BaTiO3(110)Heterostructured Multiferroics

V. Gorige * , A. Swain, K. Komatsu, M. Itoh,and T. Taniyama
Journal Articles Phys. Status Solidi -RRL (Rapid Research Letters) 11, 1700294 (2017)

Magnetization reversal has been demonstrated in an Fe layer grown on BaTiO3(110) single crystal substrate by utilizing the interface magnetic anisotropy induced by lattice strain and a small magnetic field bias. The polar plots of normalized remanent magnetization show isotropic nature at room temperature (293 K), while those at 230 and 175 K exhibit twofold symmetry with the easy axis oriented along [-111]pc of BaTiO3. Cooling and heating cycles in the range of 150–325 K in an applied magnetic field of -35 Oe along [-111]pc enable to achieve the deterministic 180 degree magnetization reversal, where distinct magnetic anisotropies of Fe associated with different structural phases of BaTiO3 will be the driving force that induces the magnetization reversal. Electric field dependence of the magnetic coercivity shows hysteric behavior, which we attribute to the combined interfacial effect of magnetization rotation in Fe and ferroelectric polarization switching in BaTiO3.

(30) Strain mediated magnetoelectric coupling in NiFe2O4-BaTiO3 multiferroic composite

V. Gorige * , R. Kati, D. H. Yoon and P. S. Anil Kumar
Journal Articles J. Phys. D: Appl. Phys. 49, 405001 (2016)

In this paper we demonstrate significant magnetoelectric coupling in ferrimagnetic, NiFe2O4, and ferroelectric, BaTiO3, multiferroic composite bulk materials by measuring temperature dependent magnetization. X-ray diffraction, scanning electron microscopy and high resolution transmission electron microscopy data show that the two phases coexist with a highly crystalline and sharp interface without any detectable impurities, which enables significant magnetoelectric (ME) coupling. The temperature dependent magnetization data of the composite clearly show the jumps in magnetization curves at the structural phase transitions of BaTiO3, thereby indicating their origin in ME coupling. The change in coercivity of composite sample in different ferroelectric phases of BaTiO3 has been observed compared to the NiFe2O4 sample. The different lattice strains corresponding to different ferroelectric phases of BaTiO3 could be the driving force for modulating the magnetization and coercivity of the composite material. This is clear evidence of strain mediated ME coupling in ferrimagnetic and ferroelectric composite materials.

(29) Effect of Zn substitution on the structural and magnetic properties of Ni-Co ferrites

K. Raju, G. Venkataiah, and D. H. Yoon
Journal Articles Ceramics International 40, 9337 (2014)

A series of ferrite samples with the compositional formula, Ni0.5Co0.5−xZnxFe2O4 (0≤x≤0.5), was prepared using the citrate based sol–gel method for the better understanding of zinc doping on the structural and magnetic properties. The Rietveld-refined X-ray diffraction data revealed that the samples are having cubic structure with the Fd-3m space group. The lattice parameter increased linearly with increasing Zn content. The surface morphology and stoichiometric ratio of the compositional elements were analyzed by scanning electron microscopy equipped with energy dispersive spectroscopy (EDS). EDS showed that the elemental ratios were stoichiometric. An examination of the magnetic properties revealed an increase in saturation magnetization with increasing Zn concentration up to x=0.3 and a decrease thereafter. These results could be explained using Neel׳s collinear two-sub-lattice model and three-sub-lattice non-collinear model suggested by Yafet and Kittel. The magnetic cubic anisotropy constant determined by the law of approach to saturation decreased with increasing Zn content. The underlying mechanism behind observed behavior was discussed qualitatively.

(28) Magnetic, electric and thermoelectric behavior of electron-doped La1-xSbxMnO3 (x = 0.05, 0.10 and 0.15) manganites

G. Venkataiah, J. C. A. Huang, P. Venugopal Reddy
Journal Articles J. Alloys Compd. 562, 128 (2013)

A systematic investigation of magnetic, electric and thermoelectric properties of sol–gel prepared electron-doped La1-xSbxMnO3 (x = 0.05, 0.10 and 0.15) was undertaken to understand the magnetotransport behavior. The X-ray diffraction and X-ray photoelectron spectroscopy measurements confirm that the samples with x = 0.05 and 0.10 are having single phase, while x = 0.15 shows a secondary phase. The second phase observed in the sample is found to have considerable influence on the magnetic and electrical transport behavior. The magnetic and electrical transport properties in low temperature ferromagnetic region may be explained in terms of spin waves and phonons, while in the paramagnetic region the adiabatic small polaron model is invoked. These materials are found to exhibit magnetoresistance values ranging from 30% to 40% and 55% to 65% at 3 and 7 T magnetic fields respectively.

(27) Electric-voltage control of magnetism in Fe/BaTiO3 heterostructured multiferroics

G. Venkataiah, E. Wada, H. Taniguchi, M. Itoh, and T. Taniyama
Journal Articles J. Appl. Phys. 113, 17C701 (2013)

Electric field (E) control of the magnetic anisotropy and coercivity (HC) of a Fe film in Fe/BaTiO3 (BTO) is demonstrated at room temperature in the tetragonal phase of BTO. Polarizing microscopy and x-ray diffraction analysis of BTO (001) surface show distinctly two different regions; one with a1, a2 and c domains separated by 180° and 90° domain boundaries (DBs) (region 1) and the other with a1 domains separated by 180° DBs (region 2). The Fe film on region 1 shows complex magnetic anisotropy with the net magnetic easy axis in between [100] and [110] directions of BTO, while the magnetic anisotropy in region 2 exhibits two fold symmetry with an easy axis along [100]. In applied electric field (±10 kV/cm), the magnetic easy axis of the Fe film in region 1 is switched to the [110] direction of BTO, whereas in region 2 it stays unaffected. The HC versus E curves in region 1 show a butterfly-like behavior, while in region 2 no changes are observed. Also, the HC measured in E = ±10 kV/cm at different magnetic field orientations shows dramatic changes in region 1 compared to region 2. The observed electric field dependent magnetic response in both regions can be understood based on the DBs modifications and associated strain effects.

(26) Formation of regular magnetic domain patterns with alternating uniaxial and biaxial anisotropy in epitaxial Fe films on BaTiO3

T. H. E. Lahtinen, Y. Shirahata, L. Yao, K. J. A. Franke, G. Venkataiah, T. Taniyama, and S. van Dijken
Journal Articles Appl. Phys. Lett. 101, 262405 (2012)

We report on domain formation and magnetization reversal in epitaxial Fe films on ferroelectric BaTiO3 substrates with ferroelastic a–c stripe domains. The Fe films exhibit biaxial magnetic anisotropy on top of c domains with out-of-plane polarization, whereas the in-plane lattice elongation of a domains induces uniaxial magnetoelastic anisotropy via inverse magnetostriction. The strong modulation of magnetic anisotropy symmetry results in full imprinting of the a–c domain pattern in the Fe films. Exchange and magnetostatic interactions between neighboring magnetic stripes further influence magnetization reversal and pattern formation within the a and c domains.

(25) Ferromagnetism in Tb doped ZnO nanocrystalline films

W. Q. Zou, C. N. Ge, G. Venkataiah, H. L. Su, H. S. Hsu, J. C. A. Huang, X.C. Liu, F. M. Zhang, and Y. W. Du
Journal Articles J. Appl. Phys. 111, 113704 (2012)

Nanocrystalline Tb-doped ZnO films have been prepared by ion-beam sputtering technique. Magnetic characterization showed that the films are ferromagnetic with Curie temperature (TC) higher than room temperature. By further treated with a rapid thermal annealing process, both the grain size and the carrier concentration of the films increase, while the saturation magnetization of the films decreases. This magnetic behavior can be hardly explained by either bound magnetic polaron model or free carrier mediation model, thus suggests that the grain boundaries play a key role for the origin of ferromagnetism in these films.

(24) Strain induced reversible and irreversible magnetization switching in Fe/BaTiO3 heterostructures

G. Venkataiah, Y. Shirahata, I Suzuki, M. Itoh, and T. Taniyama
Journal Articles J. Appl. Phys. 111, 033921 (2012)

Magnetization switching of an Fe film in Fe/BaTiO3 heterostructures is demonstrated due to the interface lattice distortion caused by the structural phase transition of BaTiO3. The temperature dependence of in-plane magnetization of the Fe film in both zero and a small negative applied magnetic field clearly reveals that the reversible and irreversible magnetization switching processes occur in the Fe/BaTiO3 heterostructures. The variation in the magnetization orientation is corroborated by the fact that the symmetry of the magnetic anisotropy changes as the BaTiO3 undergoes the structural phase transition from the tetragonal to orthorhombic phases.

(23) Manipulation of magnetic coercivity of Fe film in Fe/BaTiO3 heterostructure by electric field

G. Venkataiah, Y. Shirahata, M. Itoh, and T. Taniyama
Journal Articles Appl. Phys. Lett. 99, 102506 (2011)

The manipulation of magnetism at Fe/BaTiO3 interfaces is demonstrated via lattice distortion induced by thermal and electrical means. We find that the magnetic coercivity shows similar electric field dependence for positive and negative electric fields in the tetragonal phase of BaTiO3, whereas those in the orthorhombic and rhombohedral phases vary asymmetrically with respect to the polarity. The temperature dependent magnetization also reveals that the effect has its origin in the strong magnetoelastic coupling at the interface. The underlying mechanisms of the electric field dependence of the coercivity are discussed, associated with the different ferroelectric poling processes of BaTiO3.

(22) Switching of the symmetry of magnetic anisotropy in Fe/BaTiO3 heterostructures

Y. Shirahata, T. Nozaki, G. Venkataiah, H. Taniguchi, M. Itoh, and T. Taniyama
Journal Articles Appl. Phys. Lett. 99, 022501 (2011)

Switching of the symmetry of magnetic anisotropy is clearly demonstrated in an epitaxial Fe layer on BaTiO3, in association with the interface lattice distortion occurred at the structural phase transition of BaTiO3. The polar plot of the normalized remanent magnetization shows the fourfold symmetry with the magnetization easy axis along [100] of Fe at room temperature, while that at 230 K exhibits the twofold symmetry with the easy axis along [110]. Spatially resolved micro-Raman inspection corroborates the fact that the change in the magnetic symmetry arises from the magnetoelastic coupling at the interface.

(21) Suppression of charge ordering phenomena in nanoscale Nd0.67Ca0.33MnO3 manganite system

K. Raju, G. Venkataiah, D. C. Krishna, Y. K. Lakshmi, and P. V. Reddy
Journal Articles Phys. Lett. A 374, 4937 (2010)

A systematic investigation of electrical, magnetic and elastic properties was undertaken in nano and microcrystalline Nd0.67Ca0.33MnO3 manganite, mainly to understand the charge ordering phenomenon. There is a clear and distinct behaviour in the electrical and magnetic properties of nano and microcrystalline samples and the observed behaviour is explained.

(20) Microstructure and magnetic properties of Ni:ZnO nanorod/Zn:NiO nanowall composite structures

G. Venkataiah, M. R. S. Huang, H. L. Su, C. P. Liu, and J. C. A. Huang
Journal Articles J. Phys. Chem. C 114, 16191 (2010)

The microstructure, growth mechanism, and ferromagnetic (FM)/antiferromagnetic (AFM) coupling have been discussed in Ni:ZnO nanorod/Zn:NiO nanowall composite structures. The composite structures were synthesized by a hydrothermal method at 90 °C. A systematic investigation of high-resolution transmission electron microscopy, X-ray absorption spectroscopy, and magnetization studies reveals that the as-synthesized product shows FM behavior at room temperature, whereas the annealed sample shows mixed (FM/AFM) magnetic behavior. A detectable magnetic exchange coupling between FM/AFM has been demonstrated by magnetization measurements in the annealed products. The observed room-temperature FM behavior in these nanostructures was interpreted in terms of bound magnetic polarons.

(19) Reduced room-temperature ferromagnetism in intermediate conducting regime of V doped ZnO

S.H. Liu, H.S. Hsu, G. Venkataiah, X. Qi, C. R. Lin, J. F. Lee, K. S. Liang, and J. C. A. Huang
Journal Articles Appl. Phys. Lett., 96, 262504 (2010)

The mechanism of room temperature (RT) ferromagnetism for low doping concentration of 2.5% V in ZnO have been systematically discussed by measuring structural, electrical, and magnetic properties. The evolution of the Curie temperature from above RT in insulated V:ZnO powders to 270 K in semiconducting samples was observed with increasing carrier concentration by using different hydrogenated annealing treatment. The results provide a direct observation that the free carriers suppress the ferromagnetism and might be associated the phenomena of charge-transfer and interaction between bound magnetic polarons.

(18) Low temperature resistivity minimum and its correlation with magnetoresistance in La0.67Ba0.33MnO3 nano manganites

G. Venkataiah, J. C. A. Huang, and P. V. Reddy
Journal Articles J. Magn. Magn. Mater. 322, 417 (2010)

A systematic investigation of structural, magnetic and electrical properties of nanocrystalline La0.67Ba0.33MnO3 materials, prepared by citrate gel method has been undertaken. The temperature-dependant low-temperature resistivity in ferromagnetic metallic (∼50 K) phase shows upturn behavior and is suppressed with applied magnetic field. The experimental data (<75 K) can be best fitted in the frame work of Kondo-like spin-dependant scattering, electron–electron and electron–phonon interactions. It has been found that upturn behavior may be attributed to weak spin disorder scattering including both spin polarization and grain boundary tunneling effects, which are the characteristic features of extrinsic magnetoresistance behavior, generally found in nanocrystalline manganites. The variation of electrical resistivity with temperature in the high temperature ferromagnetic metallic part of electrical resistivity (75KTP) of resistivity data has been explained based on adiabatic small polaron hopping mechanism.

(17) Magnon drag contribution to thermopower of Nd0.67Sr0.33MnO3 nano crystalline manganites

G. Venkataiah, and P. V. Reddy
Journal Articles J. Appl. Phys. 106, 033706 (2009)

With a view to investigate the influence of nanosize on thermopower behavior of Nd0.67Sr0.33MnO3 manganites, a systematic investigation of their temperature dependent thermoelectric power (TEP) studies has been undertaken. For this purpose, the samples with different particle sizes were prepared by the sol-gel method by sintering at four different temperatures (viz., 800, 900, 1000, and 1100 °C). The average crystallite sizes were calculated using a modified Scherrer’s formula. The ferromagnetic metallic (FMM) part of the TEP data were fitted to an equation containing diffusion, magnon drag, and phonon drag terms. The relative weights of these contributions were estimated and it has been found that the magnon drag contribution predominantly contributes to the TEP in the FMM region. The phonon drag process in the samples of the present investigation is found to be dominant along the direction of cell parameter “a” than the other two directions. Finally, the paramagnetic insulting part of the TEP data has been analyzed by using small polaron hopping mechanism.

(16) Magnetoelectric behavior of sodium doped lanthanum manganites

Y.K. Lakshmi, G. Venkataiah, and P. V. Reddy
Journal Articles J. Appl. Phys. 106, 023707 (2009)

Nanocrystalline samples of sodium doped manganites with compositional formula La1−xNaxMnO3 (0.025⩽x⩽0.25)were prepared by polyvinyl alcohol assisted precursor method. After characterizing the samples by x-ray diffraction and transmission electron microscopy a systematic investigation of electrical, magnetic, and thermopower properties has been undertaken. The resistivity data were analyzed using effective medium approximation. From the analysis it has been found that the metallic fraction is increasing up to x=0.10 and remains constant with further doping. A close examination of the resistivity data clearly indicates that the sodium doped samples are slowly transformed from colossal magnetoresistance behavior to charge ordering behavior. Thermoelectric power data at low temperatures were analyzed by considering the magnon drag concept, while the high temperature data were explained by small polaron conduction mechanism.

(15) Variation of thermoelectric power with crystallite size of La0.67Sr0.33MnO3 manganites

G. Venkataiah, and P. V. Reddy
Journal Articles Phase Transitions 82, 156 (2009)

Thermoelectric power (TEP) studies of La0.67Sr0.33MnO3 polycrystalline manganite material system having varying particle size have been undertaken. These materials were prepared by citrate based sol–gel route by sintering at four different temperatures and were later characterized by X-ray diffraction (XRD), scanning electron microscopy, electrical resistivity, AC susceptibility, etc., studies. The XRD data were analyzed by Rietveld refinement technique. Thermopower versus temperature plots are found to exhibit two peaks and an effort has been made to explain the significance of both of them. Finally, with a view to understand the conduction mechanism in these materials, TEP data in the low-temperature ferromagnetic metallic (T < T P) regime were analyzed using electron–magnon scattering phenomenon, while that in the high-temperature insulating (T > T P) region were analyzed by small polaron hopping model.

(14) Magnetic and electrical behavior of La1-xAxMnO3 (A = Li,Na,K and Rb) manganites

Y. K. Lakshmi, G. Venkataiah, and P. V. Reddy
Journal Articles Physica B 403, 3059 (2008)

Abstract

(13) Electrical transport properties of Nd0.67-xEuxSr0.33MnO3 (0£x£0.67) manganites

G. Venkataiah, and P. V. Reddy
Journal Articles J. Mater. Sci. 43, 4760 (2008)

Abstract

(12) Influence of sintering temperature on resistivity, magnetoresistance and thermopower of La0.67Ca0.33MnO3

G. Venkataiah, Y. K. Lakshmi, and P. V. Reddy
Journal Articles PMC Physics B 1, 7 (2008)

Abstract

(11) Influence of cation mismatch on electrical, magnetic and　magnetoresistance properties of Pr0.67A0.33MnO3 manganite system

G. Venkataiah, and P. V. Reddy
Journal Articles Phys. Stat. Sol. (a) 204, 1192 (2007)

Abstract

(10) Influence of particle size on electrical transport properties of La0.67Sr0.33MnO3 manganite system

G. Venkataiah, Y. K. Lakshmi, V. Prasad, and P. V. Reddy
Journal Articles J. Nanosci. Nanotechnol. 7, 2000 (2007)

Abstract

(9) Thermopower studies of Pr0.67D0.33MnO3 manganite system

G. Venkataiah, Y. K. Lakshmi, and P. V. Reddy
Journal Articles J. Phys. D:Appl. Phys. 40, 721 (2007)

Abstract

(8) Anomalous variation of magnetoresistance in Nd0.67-yEuySr0.33MnO3 manganites

G. Venkataiah, V. Prasad, and P. V. Reddy
Journal Articles Solid State Commun. 141, 73 (2007)

Abstract

(7) Electrical behavior of some rare earth doped Nd0.33Ln0.34Sr0.33MnO3 manganites, J. Magn. Magn. Matter. 309, 237 (2007).

K. Padmavathi, G. Venkataiah, and P. V. Reddy
Journal Articles J. Magn. Magn. Matter. 309, 237 (2007)

Abstract

(6) Influence of A-site cation mismatch on structural, magnetic and electrical properties of lanthanum manganites

G. Venkataiah, V. Prasad, and P. V. Reddy
Journal Articles J. Alloys Compd. 429, 1 (2007)

Abstract

(5) Structure and electrical transport of some Cd-doped La0.67Sr0.33MnO3 manganites

G. Venkataiah, V. Prasad, and P. V. Reddy
Journal Articles Phys. Stat. Sol. (a) 203, 2478 (2006)

Abstract

(4) Electrical behavior of some lanthanum based rare earth CMR materials

V. R. Kumari, G. Venkataiah, and P. V. Reddy
Journal Articles Int. J. Mod. Phys. B 19, 3619 (2005)

Abstract

(3) Structural, magnetic and magnetotransport behavior of some Nd-based perovskite manganites

G. Venkataiah, and P. V. Reddy
Journal Articles Solid State Commun. 136, 114 (2005)

Abstract

(2) Effect of sintering temperature on electrical transport properties of La0.67Ca0.33MnO3

G. Venkataiah, D. C. Krishna, M. Vithal, S. S. Rao, S. V. Bhat, V. Prasad, S. V. Subramanyam, and P. V. Reddy
Journal Articles Physica B 357, 370 (2005)

Abstract

(1) Electrical behavior of sol-gel prepared Nd0.67Sr0.33MnO3 manganite system

G. Venkataiah, and P. V. Reddy
Journal Articles J. Magn. Magn. Mater. 285, 343 (2005)

Abstract

Influence of sintering temperature on magnetotransport behavior of some nanocrystalline manganites

G. Venkataiah, Y. K. Lakshmi, and P. V. Reddy
Articles/Chapters in Edited Books Sintering - Methods and Products (ISBN 979-953-307-041-3) InTech-Open Access Publishers, Chapter no. 13, Page no. 267 (2012)

Guest lecture on "Magnetism and its applications"

Magnetism and its applications
Conferences & Guest Lectures Held at Department of Physics, Telangana University (South Campus), Nizamabad, Telangana, India. During October 30, 2014

Abstract

International Conference on Magnetic Materials and Applications (ICMAGMA-2014)

Oral Presentation: Strain mediated magnetoelectric coupling in ferrite-ferroelectric multiferroic composites
Conferences & Guest Lectures Held at Department of Physics, Pondicherry University, Pondicherry, India. During September 15-17, 2014

Abstract

National Conference on Absorption and Magnetic Resonance Spectroscopy and their Integration to Sustainable Human Development” (NCAMRS-SHD-2014)

Invited talk, Electric field control of magnetism: Ultra-low power device applications
Conferences & Guest Lectures Held at Department of Physics, Osmania University, Hyderabad, India. During August 30-31, 2014

Abstract

Internal conference on ‘Advancements in Materials, Health and Safety towards Sustainable Energy & Environment (MHS-2014)

Poster Presentation, Electric field Control of Magnetism in Ferromagnetic/Ferroelectric Heterostructures
Conferences & Guest Lectures Held at Chennai, India. During August 07-08, 2014

Abstract

International Union of Materials Research Society-International Conference in Asia 2013 (IUMRS-ICA 2013)

Poster Presentation, Strain mediated magnetoelectric coupling in NiFe2O4-BaTiO3 multiferroic composite (won best poster award)
Conferences & Guest Lectures Held at IISc, India. During December, 16-20, 2013

Abstract

12th Joint MMM/Intermag Conference

Poster Presentation, Electric-voltage control of magnetism in Fe/BaTiO3 heterostructured multiferroics
Conferences & Guest LecturesHeld at Chicago, USA. During January 14-18th, 2013

Abstract

The Physical Society Japan 66th Annual Meeting

Poster Presentation, Title: Electric field control of magnetic coercivity of Fe thin film in Fe/BaTiO3 heterostructures
Conferences & Guest Lectures Held at Osaka, JAPAN. During March 24rd - 27th, 2012

Abstract

56th Annual Conference on Magnetism and Magnetic Materials (MMM 2011)

Poster Presentation, Title: Electric field control of magnetic anisotropy in Fe/BaTiO3
Conferences & Guest Lectures Held Scottsdale, Arizona, USA. During October 30-November 3, 2011

Abstract

Teaching

Currrent Teaching

  • Jul-2020 Dec-2020

    Mechanics Lab(PY102)

Teaching History

  • Jan-2020 Jun-2020

    (a) Structure and Properties of Matter (IPYT 602)

    (b) Laboratory-IV (Microwave & Nuclear Physics) (PY552)

  • Jul-2019 Dec-2019

    (a) Solid State Physics Lab(PY505)

    (b) Electronics for All (FN119)

  • Jan-2019 Jun-2019

    (a) Structure and Properties of Matter (IPYT 602)

    (b) Laboratory-IV (Microwave & Nuclear Physics)

  • Jul-2018 Dec-2018

    Electronics (IPYT 502)

  • Jan-2018 Jun-2018

    Structure and Properties of Matter (IPYT 602)

    Physical Constants Measurements Lab (IPYL 606)

  • Jul-2017 Dec-2017

    Electricity and Magnetism Lab (IPYL 302)

  • Jan-2017 Jun-2017

    (a) Basics of Condensed Matter (PY354)

    (b) Laboratory-IV (Microwave & Nuclear Physics)

  • July-2016 Dec-2016

    General Properties of Matter (IPY302)

  • Jan-2016 Jun-2016

    (a) Microwave Laboratory (PY552)

    (b) Probes of Condensed Matter(PY573)

  • Jul-2015 Dec-2015

    (a) Electronic Circuits Laboratory (PY406)

    (b) General Properties of Matter (PY302)

    (c) Electronics lab-SCIS

  • Jan-2015 Jun-2015

    (a) Physical Property Measurements Laboratory (IPY355)

    (b) Microwave Laboratory (PY552)

  • Jul-2014 Dec-2014

    (a) Electronic Circuits Laboratory (PY406)

    (b) Mechanics Laboratory (PY102)

  • Jan-2014 Jun-2014

    Microwave Laboratory (PY552)

Wecome to join with MMM group

We are looking for highly motivaed PhD, Postgraduate, Undergraduates and Visiting students

Position vacancy for the year 2017

'PhD' [1]

'Postgraduate' [0]

'Undergraduate' [0]

'Visiting students' [2]

Contact Address

Dr Venkataiah Gorige

Assistant Professor

School of Physics

University of Hyderabad

Prof. C R Rao Road, Gachibowli

Hyderabad, 500046, INDIA

  •    +91 40 23134303 (Office)
  •    +91 40 23010227 (Fax.)
  •    vgsp@uohyd.ernet.in
  •    vgsp@uohyd.ac.in