Ravindranath Viswan - Profile on Academia.edu (original) (raw)
Papers by Ravindranath Viswan
Physica Status Solidi A-applications and Materials Science, Jun 18, 2012
A sensitive tuning of dielectric properties under the application of magnetic field in Fe 74.4 Co... more A sensitive tuning of dielectric properties under the application of magnetic field in Fe 74.4 Co 21.6 Si 0.5 B 3.3 Mn 0.1 C 0.1 /0.7Pb-(Mg 1/3 Nb 2/3)O 3-0.3PbTiO 3 multiferroic composites is presented. We demonstrate large variations of the effective permittivity at resonance region under extremely low magnetic field of 4 Oe near room temperature. The tuning of the maximum dielectric permittivity at resonance and the corresponding frequency was systematically studied. We suggest that the magnetic dependence of the effective permittivity is consistent with a strain-mediated magnetic-elasto-dielectric effect. Our results suggest a route towards future applications of the dielectric properties tuning effect in advanced devices.
Journal of Applied Physics, Jul 1, 2012
Applied Physics Letters, 2012
We deposited NaNbO 3 (NNO)-Nb 2 O 5 (NO) self-assembled heterostructures on LaAlO 3 (LAO) to form... more We deposited NaNbO 3 (NNO)-Nb 2 O 5 (NO) self-assembled heterostructures on LaAlO 3 (LAO) to form ferroelectric-semiconductor vertically integrated nanostructures. The NNO component formed as nanorods embedded in a NO matrix. X-ray diffraction confirmed epitaxial growth of both NNO and NO phases. Phase distribution was detected by scanning electron microscopy. The NNO/NO volume ratio was strongly dependent on the deposition temperature due to the volatility of sodium. Piezoelectric force microscopy revealed a good piezoelectric response in the NNO component with a piezoelectric coefficient of D 33 % 12 pm/V, with SrRuO 3 (SRO) acting as bottom electrode. The current-voltage characterization of NNO-NO/SRO-LAO showed a typical diode rectifying behavior.
Engineered Magnetic Shape Anisotropy in BiFeO3–CoFe2O4 Self-Assembled Thin Films
ACS Nano, 2013
We report growth of various phase architectures of self-assembled BiFeO3-CoFe2O4 (BFO-CFO) thin f... more We report growth of various phase architectures of self-assembled BiFeO3-CoFe2O4 (BFO-CFO) thin films on differently oriented SrTiO3 (STO) substrates. CFO forms segregated square, stripe, and triangular nanopillars embedded in a coherent BFO matrix on (001)-, (110)-, and (111)-oriented STO substrates, respectively. Nanostructures with an aspect ratio of up to 5:1 with a prominent magnetic anisotropy were obtained on both (001) and (110) STO along out-of-plane and in-plane directions. Magnetic easy axis rotation from in-plane to out-of-plane directions was realized through aspect ratio control. An intractable in-plane anisotropy was fixed in CFO on (111) STO due to the triangular shape of the ferromagnetic phase nanopillars. These studies established a detailed relationship of magnetic anisotropy with specific shape and dimensions of ordered magnetic arrays. The results suggest a way to effectively control the magnetic anisotropy in patterned ferromagnetic oxide arrays with tunable shape, aspect ratio, and elastic strain conditions of the nanostructures.
Linear RF Ion Source for a Wide Range of Plasma Processing Applications
65th Annual Technical Conference Proceedings
Scientific Reports
The coupling between the tetragonal phase (T-phase) of BiFeO 3 (BFO) and CoFe 2 O 4 (CFO) in magn... more The coupling between the tetragonal phase (T-phase) of BiFeO 3 (BFO) and CoFe 2 O 4 (CFO) in magnetoelectric heterostructures has been studied. Bilayers of CFO and BFO were deposited on (001) LaAlO 3 single crystal substrates by pulsed laser deposition. After 30 min of annealing, the CFO top layer exhibited a T-phase-like structure, developing a platform-like morphology with BFO. Magnetic hysteresis loops exhibited a strong thickness effect of the CFO layer on the coercive field, in particular along the out-of-plane direction. Magnetic force microscopy images revealed that the T-phase CFO platform contained multiple magnetic domains, which could be tuned by applying a tip bias. A combination of shape, strain, and exchange coupling effects are used to explain the observations. Magnetoelectricity (ME) is a coupling between magnetic and polar order parameters 1. It makes possible the manipulation of the magnetic spins by an applied electric field, offering potential for sensors and spintronic devices 2-4. Such ME coupling has been reported in both single-phase and composite materials, which has attracted significant interest around the world 2,5. Normally, single-phase ME materials are considered as multiferroics with two coexisting orders. Strain-mediated ME composites made of magnetostrictive and piezoelectric materials have a much stronger ME coupling, relative to single-phase systems. The spinel CoFe 2 O 4 (CFO) is a typical ferrimagnetic oxide that has a high saturation magnetization, high Curie temperature, and large magnetocrystalline anisotropy 6-8. Combined with its large magnetostriction coefficient (λ 100 : −250 to −590 × 10 −6), CFO is a good choice for the magnetostrictive phase in ME composites 8,9. Alternatively, BiFeO 3 (BFO) is the only known single phase room temperature multiferroic material. It has coexisting antiferromagnetic (Neel temperature T N ~ 643 K) and ferroelectric (Curie temperature T C ~ 1103 K) orders 10,11 , leading to a weak linear (intrinsic) ME coupling via the Dzyaloshinskii-Moriya interaction 12. When used in a composite material, the polarization of BFO can couple to the magnetostriction of CFO, resulting in large quadratic (extrinsic) ME coupling via strain 13. Since BFO is antiferromagnetic, at its interface with other ferromagnetic materials, an exchange coupling exists 14. The coupling between BFO and other ferromagnetic metals or alloys, such as Co 15,16 and CoFe 17 , has been considered. However, such oxide/metal heterostructures are not ideal due to incompatibilities between dissimilar material types 18. To overcome this limitation, all-oxide systems have been proposed, such as Fe 3 O 4 /BFO 18 and La 0.67 Sr 0.33 MnO 3 /BFO 19. Accordingly, an exchange coupling can be expected in CFO/BFO nanocomposites at their ferrimagnetic/antiferromagnetic interfaces 20. Nanocomposites of CFO/BFO self-assemble into a vertically integrated nanopillar structure that results from an immiscibility and lattice mismatch between CFO and BFO phases 7,13. All prior investigations of self-assembled nanocomposites have focused on the rhombohedral phase (R-phase) of BFO with CFO 7,13,20,21. A tetragonal phase (T-phase) of BFO is also known to exist when deposited on LaAlO 3 (LAO) substrates, which has a very high c/a ratio 22. However, CFO/T-phase BFO nanocomposites have not yet been reported. The T-phase of BFO exhibits unique property characteristics, relative to the R-phase. For example, the antiferromagnetic order in the T-phase changes from G-type (R-phase) to C-type, while the ferroelectric polarization direction rotates from [111] (R-phase) to [001] 21-24. Here, CFO/T-phase BFO nanocomposites were fabricated on (001) LAO substrates by pulsed laser deposition (PLD), and its ME properties were compared with that of CFO/R-phase BFO ones on (001) SrTiO 3 (STO) substrates.
E-field controlled phase transformation in bismuth ferrite thin films, and effect of laser energy density
Applied Physics Letters
Scientific Reports
We have deposited self-assembled BiFeO 3-CoFe 2 O 4 (BFO-CFO) thin films on (100)-oriented SrRuO ... more We have deposited self-assembled BiFeO 3-CoFe 2 O 4 (BFO-CFO) thin films on (100)-oriented SrRuO 3buffered Pb(Mg 1/3 Nb 2/3) 0.62 Ti 0.38 O 3 (PMN-38PT) single crystal substrates. These heterostructures were used for the study of real-time changes in the magnetization with applied DC electric field (E DC). With increasing E DC , a giant magnetization change was observed along the out-of-plane (easy) axis. The induced magnetization changes of the CFO nanopillars in the BFO/CFO layer were about ΔM/ M rDC = 93% at E DC = −3 kv/cm. A giant converse magnetoelectric (CME) coefficient of 1.3 × 10 −7 s/m was estimated from the data. By changing E DC , we found multiple(N ≥ 4) unique possible values of a stable magnetization with memory on the removal of the field.
Sensors and Actuators A: Physical, 2015
This paper describes the fabrication and performance results of a magnetoelectric macro fiber com... more This paper describes the fabrication and performance results of a magnetoelectric macro fiber composite (ME MFC). The magnetoelectric composite was fabricated by bonding a magnetostrictive layer to a piezoelectric layer using a novel approach of low temperature transient liquid phase (LTTLP) bonding. The composite was diced into 150 micron wide fibers and bonded to a custom designed copper flexible circuit using a spin coated low viscosity room temperature curing epoxy. ME MFC's with varying ferrite thicknesses of 0.6 mm and 0.5 mm were fabricated and characterized for energy harvesting. The composite with 0.6mm ferrite thickness achieved an open circuit voltage of 101 mV (ME voltage coefficient of 6740 mV/cmOe) and peak power of 3.1 nW across 356 kΩ matching load at 264 Hz.
Theoretical and experimental investigation of magnetoelectric effect for bending-tension coupled modes in magnetostrictive-piezoelectric layered composites
Journal of Applied Physics
In this paper, we discuss a theoretical model with experimental verification for the resonance en... more In this paper, we discuss a theoretical model with experimental verification for the resonance enhancement of magnetoelectric (ME) interactions at frequencies corresponding to bending-tension oscillations. A dynamic theory of arbitrary laminated magneto-elasto-electric bars was constructed. The model included bending and longitudinal vibration effects for predicting ME coefficients in laminate bar composite structures consisting of magnetostrictive, piezoelectric, and pure elastic layers. The thickness dependence of stress, strain, and magnetic and electric fields within a sample are taken into account, as such the bending deformations should be considered in an applied magnetic or electric field. The frequency dependence of the ME voltage coefficients has obtained by solving electrostatic, magnetostatic, and elastodynamic equations. We consider boundary conditions corresponding to free vibrations at both ends. As a demonstration, our theory for multilayer ME composites was then app...
EFFECT OF ADDITION OF 5 WT% PbO ON THE MICROSTRUCTURE AND ELECTRICAL TRANSPORT PROPERTIES OF La~ 0~.~ 7Ca~ 0~.~ 3MnO~ 3
Method for preparation of hybrid comprising magnetite nanoparticles and carbon nitride nanotubes
Voltage-controlled magnetization reversal writing type magnetic random access memory device and method of writing and reading information using the same
B. B€ uchner, and R. Gross
Direct observation of substrate temperature dependent domain evolution pattern in FePt alloy thin films
INTERMAG 2006 - IEEE International Magnetics Conference, 2006
ABSTRACT In the present study, the magnetic domain reversal patterns in equiatomic FePt thin film... more ABSTRACT In the present study, the magnetic domain reversal patterns in equiatomic FePt thin films were investigated in real time using a magneto-optical microscope magnetometer (MOMM) with respect to the substrate temperature during film deposition.
Ferroelectrics - Material Aspects, 2011
Solid State Communications, 2001
The nature of the insulating regime in certain Pr-and La-based manganites having ferromagnetic tr... more The nature of the insulating regime in certain Pr-and La-based manganites having ferromagnetic transition temperatures (T C) close to room temperature (RT) and at T C ! RT was studied. It is seen that in a small temperature regime close to T C and/or T P (peak resistivity temperature) the conduction mechanism is of the 3D-variable range hopping (VRH) type while far away from T P , the insulating regime is governed by an Arrhenius and/or polaronic type of behaviour. In the presence of a magnetic ®eld the resistivity data do not ®t well to either the VRH or the polaron mechanisms, however, a better ®t is obtained using the magnetic localization model. Inverse ac-susceptibility (x 0) vs temperature curves show a deviation from the Curie±Weiss behaviour at a temperature (u P , paramagnetic Curie temperature) well above T C of the respective compounds, indicating the formation of superparamagnetic clusters close to RT. Our recent studies on Ho-and Y-doped manganites (La 0.72x R x Ca 0.3 MnO 3 , R Ho and Y and x 0:05; 0.075 and 0.1) unequivocally show coupling of Ho-magnetic moment with that of Mn in the lattice [Phys. Rev. B 63 (2001) 184 434].
Physical Review B, 2014
We report the growth of ferromagnetic epitaxial CoFe 2 O 4 (CFO) thin films on 011-oriented tetra... more We report the growth of ferromagnetic epitaxial CoFe 2 O 4 (CFO) thin films on 011-oriented tetragonalstructured 0.62Pb(Mg,Nb)O 3-0.38PbTiO 3 single crystal substrates. In the substrates, electric field-induced polarization reorientation resulted in maximum strains of −1.3% and 0.64% along in-plane 100 and along in-plane 011, respectively. As a consequence, in the CFO films, irreversible magnetic coercive field changes of 580, −510, and −220 Oe were observed along in-plane 100 and 011 and out-of-plane 011, respectively, after electric field poling. After annealing at 470 K, the substrate depoled, and both the magnetic coercive fields and the remnant magnetizations along the three directions recovered their original values.
physica status solidi (RRL) - Rapid Research Letters, 2012
Physica Status Solidi A-applications and Materials Science, Jun 18, 2012
A sensitive tuning of dielectric properties under the application of magnetic field in Fe 74.4 Co... more A sensitive tuning of dielectric properties under the application of magnetic field in Fe 74.4 Co 21.6 Si 0.5 B 3.3 Mn 0.1 C 0.1 /0.7Pb-(Mg 1/3 Nb 2/3)O 3-0.3PbTiO 3 multiferroic composites is presented. We demonstrate large variations of the effective permittivity at resonance region under extremely low magnetic field of 4 Oe near room temperature. The tuning of the maximum dielectric permittivity at resonance and the corresponding frequency was systematically studied. We suggest that the magnetic dependence of the effective permittivity is consistent with a strain-mediated magnetic-elasto-dielectric effect. Our results suggest a route towards future applications of the dielectric properties tuning effect in advanced devices.
Journal of Applied Physics, Jul 1, 2012
Applied Physics Letters, 2012
We deposited NaNbO 3 (NNO)-Nb 2 O 5 (NO) self-assembled heterostructures on LaAlO 3 (LAO) to form... more We deposited NaNbO 3 (NNO)-Nb 2 O 5 (NO) self-assembled heterostructures on LaAlO 3 (LAO) to form ferroelectric-semiconductor vertically integrated nanostructures. The NNO component formed as nanorods embedded in a NO matrix. X-ray diffraction confirmed epitaxial growth of both NNO and NO phases. Phase distribution was detected by scanning electron microscopy. The NNO/NO volume ratio was strongly dependent on the deposition temperature due to the volatility of sodium. Piezoelectric force microscopy revealed a good piezoelectric response in the NNO component with a piezoelectric coefficient of D 33 % 12 pm/V, with SrRuO 3 (SRO) acting as bottom electrode. The current-voltage characterization of NNO-NO/SRO-LAO showed a typical diode rectifying behavior.
Engineered Magnetic Shape Anisotropy in BiFeO3–CoFe2O4 Self-Assembled Thin Films
ACS Nano, 2013
We report growth of various phase architectures of self-assembled BiFeO3-CoFe2O4 (BFO-CFO) thin f... more We report growth of various phase architectures of self-assembled BiFeO3-CoFe2O4 (BFO-CFO) thin films on differently oriented SrTiO3 (STO) substrates. CFO forms segregated square, stripe, and triangular nanopillars embedded in a coherent BFO matrix on (001)-, (110)-, and (111)-oriented STO substrates, respectively. Nanostructures with an aspect ratio of up to 5:1 with a prominent magnetic anisotropy were obtained on both (001) and (110) STO along out-of-plane and in-plane directions. Magnetic easy axis rotation from in-plane to out-of-plane directions was realized through aspect ratio control. An intractable in-plane anisotropy was fixed in CFO on (111) STO due to the triangular shape of the ferromagnetic phase nanopillars. These studies established a detailed relationship of magnetic anisotropy with specific shape and dimensions of ordered magnetic arrays. The results suggest a way to effectively control the magnetic anisotropy in patterned ferromagnetic oxide arrays with tunable shape, aspect ratio, and elastic strain conditions of the nanostructures.
Linear RF Ion Source for a Wide Range of Plasma Processing Applications
65th Annual Technical Conference Proceedings
Scientific Reports
The coupling between the tetragonal phase (T-phase) of BiFeO 3 (BFO) and CoFe 2 O 4 (CFO) in magn... more The coupling between the tetragonal phase (T-phase) of BiFeO 3 (BFO) and CoFe 2 O 4 (CFO) in magnetoelectric heterostructures has been studied. Bilayers of CFO and BFO were deposited on (001) LaAlO 3 single crystal substrates by pulsed laser deposition. After 30 min of annealing, the CFO top layer exhibited a T-phase-like structure, developing a platform-like morphology with BFO. Magnetic hysteresis loops exhibited a strong thickness effect of the CFO layer on the coercive field, in particular along the out-of-plane direction. Magnetic force microscopy images revealed that the T-phase CFO platform contained multiple magnetic domains, which could be tuned by applying a tip bias. A combination of shape, strain, and exchange coupling effects are used to explain the observations. Magnetoelectricity (ME) is a coupling between magnetic and polar order parameters 1. It makes possible the manipulation of the magnetic spins by an applied electric field, offering potential for sensors and spintronic devices 2-4. Such ME coupling has been reported in both single-phase and composite materials, which has attracted significant interest around the world 2,5. Normally, single-phase ME materials are considered as multiferroics with two coexisting orders. Strain-mediated ME composites made of magnetostrictive and piezoelectric materials have a much stronger ME coupling, relative to single-phase systems. The spinel CoFe 2 O 4 (CFO) is a typical ferrimagnetic oxide that has a high saturation magnetization, high Curie temperature, and large magnetocrystalline anisotropy 6-8. Combined with its large magnetostriction coefficient (λ 100 : −250 to −590 × 10 −6), CFO is a good choice for the magnetostrictive phase in ME composites 8,9. Alternatively, BiFeO 3 (BFO) is the only known single phase room temperature multiferroic material. It has coexisting antiferromagnetic (Neel temperature T N ~ 643 K) and ferroelectric (Curie temperature T C ~ 1103 K) orders 10,11 , leading to a weak linear (intrinsic) ME coupling via the Dzyaloshinskii-Moriya interaction 12. When used in a composite material, the polarization of BFO can couple to the magnetostriction of CFO, resulting in large quadratic (extrinsic) ME coupling via strain 13. Since BFO is antiferromagnetic, at its interface with other ferromagnetic materials, an exchange coupling exists 14. The coupling between BFO and other ferromagnetic metals or alloys, such as Co 15,16 and CoFe 17 , has been considered. However, such oxide/metal heterostructures are not ideal due to incompatibilities between dissimilar material types 18. To overcome this limitation, all-oxide systems have been proposed, such as Fe 3 O 4 /BFO 18 and La 0.67 Sr 0.33 MnO 3 /BFO 19. Accordingly, an exchange coupling can be expected in CFO/BFO nanocomposites at their ferrimagnetic/antiferromagnetic interfaces 20. Nanocomposites of CFO/BFO self-assemble into a vertically integrated nanopillar structure that results from an immiscibility and lattice mismatch between CFO and BFO phases 7,13. All prior investigations of self-assembled nanocomposites have focused on the rhombohedral phase (R-phase) of BFO with CFO 7,13,20,21. A tetragonal phase (T-phase) of BFO is also known to exist when deposited on LaAlO 3 (LAO) substrates, which has a very high c/a ratio 22. However, CFO/T-phase BFO nanocomposites have not yet been reported. The T-phase of BFO exhibits unique property characteristics, relative to the R-phase. For example, the antiferromagnetic order in the T-phase changes from G-type (R-phase) to C-type, while the ferroelectric polarization direction rotates from [111] (R-phase) to [001] 21-24. Here, CFO/T-phase BFO nanocomposites were fabricated on (001) LAO substrates by pulsed laser deposition (PLD), and its ME properties were compared with that of CFO/R-phase BFO ones on (001) SrTiO 3 (STO) substrates.
E-field controlled phase transformation in bismuth ferrite thin films, and effect of laser energy density
Applied Physics Letters
Scientific Reports
We have deposited self-assembled BiFeO 3-CoFe 2 O 4 (BFO-CFO) thin films on (100)-oriented SrRuO ... more We have deposited self-assembled BiFeO 3-CoFe 2 O 4 (BFO-CFO) thin films on (100)-oriented SrRuO 3buffered Pb(Mg 1/3 Nb 2/3) 0.62 Ti 0.38 O 3 (PMN-38PT) single crystal substrates. These heterostructures were used for the study of real-time changes in the magnetization with applied DC electric field (E DC). With increasing E DC , a giant magnetization change was observed along the out-of-plane (easy) axis. The induced magnetization changes of the CFO nanopillars in the BFO/CFO layer were about ΔM/ M rDC = 93% at E DC = −3 kv/cm. A giant converse magnetoelectric (CME) coefficient of 1.3 × 10 −7 s/m was estimated from the data. By changing E DC , we found multiple(N ≥ 4) unique possible values of a stable magnetization with memory on the removal of the field.
Sensors and Actuators A: Physical, 2015
This paper describes the fabrication and performance results of a magnetoelectric macro fiber com... more This paper describes the fabrication and performance results of a magnetoelectric macro fiber composite (ME MFC). The magnetoelectric composite was fabricated by bonding a magnetostrictive layer to a piezoelectric layer using a novel approach of low temperature transient liquid phase (LTTLP) bonding. The composite was diced into 150 micron wide fibers and bonded to a custom designed copper flexible circuit using a spin coated low viscosity room temperature curing epoxy. ME MFC's with varying ferrite thicknesses of 0.6 mm and 0.5 mm were fabricated and characterized for energy harvesting. The composite with 0.6mm ferrite thickness achieved an open circuit voltage of 101 mV (ME voltage coefficient of 6740 mV/cmOe) and peak power of 3.1 nW across 356 kΩ matching load at 264 Hz.
Theoretical and experimental investigation of magnetoelectric effect for bending-tension coupled modes in magnetostrictive-piezoelectric layered composites
Journal of Applied Physics
In this paper, we discuss a theoretical model with experimental verification for the resonance en... more In this paper, we discuss a theoretical model with experimental verification for the resonance enhancement of magnetoelectric (ME) interactions at frequencies corresponding to bending-tension oscillations. A dynamic theory of arbitrary laminated magneto-elasto-electric bars was constructed. The model included bending and longitudinal vibration effects for predicting ME coefficients in laminate bar composite structures consisting of magnetostrictive, piezoelectric, and pure elastic layers. The thickness dependence of stress, strain, and magnetic and electric fields within a sample are taken into account, as such the bending deformations should be considered in an applied magnetic or electric field. The frequency dependence of the ME voltage coefficients has obtained by solving electrostatic, magnetostatic, and elastodynamic equations. We consider boundary conditions corresponding to free vibrations at both ends. As a demonstration, our theory for multilayer ME composites was then app...
EFFECT OF ADDITION OF 5 WT% PbO ON THE MICROSTRUCTURE AND ELECTRICAL TRANSPORT PROPERTIES OF La~ 0~.~ 7Ca~ 0~.~ 3MnO~ 3
Method for preparation of hybrid comprising magnetite nanoparticles and carbon nitride nanotubes
Voltage-controlled magnetization reversal writing type magnetic random access memory device and method of writing and reading information using the same
B. B€ uchner, and R. Gross
Direct observation of substrate temperature dependent domain evolution pattern in FePt alloy thin films
INTERMAG 2006 - IEEE International Magnetics Conference, 2006
ABSTRACT In the present study, the magnetic domain reversal patterns in equiatomic FePt thin film... more ABSTRACT In the present study, the magnetic domain reversal patterns in equiatomic FePt thin films were investigated in real time using a magneto-optical microscope magnetometer (MOMM) with respect to the substrate temperature during film deposition.
Ferroelectrics - Material Aspects, 2011
Solid State Communications, 2001
The nature of the insulating regime in certain Pr-and La-based manganites having ferromagnetic tr... more The nature of the insulating regime in certain Pr-and La-based manganites having ferromagnetic transition temperatures (T C) close to room temperature (RT) and at T C ! RT was studied. It is seen that in a small temperature regime close to T C and/or T P (peak resistivity temperature) the conduction mechanism is of the 3D-variable range hopping (VRH) type while far away from T P , the insulating regime is governed by an Arrhenius and/or polaronic type of behaviour. In the presence of a magnetic ®eld the resistivity data do not ®t well to either the VRH or the polaron mechanisms, however, a better ®t is obtained using the magnetic localization model. Inverse ac-susceptibility (x 0) vs temperature curves show a deviation from the Curie±Weiss behaviour at a temperature (u P , paramagnetic Curie temperature) well above T C of the respective compounds, indicating the formation of superparamagnetic clusters close to RT. Our recent studies on Ho-and Y-doped manganites (La 0.72x R x Ca 0.3 MnO 3 , R Ho and Y and x 0:05; 0.075 and 0.1) unequivocally show coupling of Ho-magnetic moment with that of Mn in the lattice [Phys. Rev. B 63 (2001) 184 434].
Physical Review B, 2014
We report the growth of ferromagnetic epitaxial CoFe 2 O 4 (CFO) thin films on 011-oriented tetra... more We report the growth of ferromagnetic epitaxial CoFe 2 O 4 (CFO) thin films on 011-oriented tetragonalstructured 0.62Pb(Mg,Nb)O 3-0.38PbTiO 3 single crystal substrates. In the substrates, electric field-induced polarization reorientation resulted in maximum strains of −1.3% and 0.64% along in-plane 100 and along in-plane 011, respectively. As a consequence, in the CFO films, irreversible magnetic coercive field changes of 580, −510, and −220 Oe were observed along in-plane 100 and 011 and out-of-plane 011, respectively, after electric field poling. After annealing at 470 K, the substrate depoled, and both the magnetic coercive fields and the remnant magnetizations along the three directions recovered their original values.
physica status solidi (RRL) - Rapid Research Letters, 2012