A miniature, quasi one dimensional, magnetic field sensor based on magnetoelectric coupling is pr... more A miniature, quasi one dimensional, magnetic field sensor based on magnetoelectric coupling is presented. The magnetoelectric sensor makes use of the d31 coupling mode between a piezoelectric lead zirconate titanate tube and FeNi magnetostrictive wire. The sensors demonstrate high sensitivity, high signal-to-noise ratio, and low noise floor at zero DC magnetic bias field and at low frequency resulting in smaller, lower power consumption, and volumetric efficiency. Experiments indicate a zero bias field sensitivity of 16.5 mV/Oe at 100 Hz stemming from a magnetoelectric coefficient of 1.65 V/cm-Oe. The results are quantitatively described by a theoretical model of laminate composites.
We design a multiferroic laminated heterostructure composed of a Fe-Ga magnetostrictive layer and... more We design a multiferroic laminated heterostructure composed of a Fe-Ga magnetostrictive layer and a PMN-PT piezoelectric layer and examine the converse magnetoelectric effect (CME). Such a heterostructure is potentially useful as a magnetic field generator, which can be used in the tuning of microwave devices. Magnetization, magnetic coercivity, remanence, and squareness exhibit pronounced hysteretic behavior and potential for tuning with an applied electric field. We obtain E = 12:5 Oe cm kV 01. The deformation of the PMN-PT under an applied electric field results in an internal stress-induced magnetic field, with an experimentally determined value of 100 Oe. The tunable range of fringe fields generated by the stress-induced field is predicted to be 104 Oe. The results will establish a foundation in the design of E-field tunable magnetic devices.
Journal of Magnetism and Magnetic Materials, Nov 1, 2012
Co 2 Z hexaferrite materials possess intrinsically high permeability, zero field ferromagnetic re... more Co 2 Z hexaferrite materials possess intrinsically high permeability, zero field ferromagnetic resonance values ($ 1 GHz), and have their magnetic orientation in the plane perpendicular to the c-axis. These characteristics make these materials practical for applications in low to mid ultra-high frequency and L-band microwave device designs. Due to the relatively large size of elements operating within these bands, it has become important to produce large amounts of Co 2 Z type hexaferrite materials. A modified co-precipitation method has been proposed to produce scalable quantities of high quality Co 2 Z hexaferrite particles, at $ 24 g/L. These particles have been thoroughly characterized by vibrating sample magnetometry (VSM) and X-ray diffraction (XRD) with regard to phase purity and magnetic properties. After formation and subsequent ball milling, to achieve single domain particles on the order of 0.5-2 um, particles were oriented and pressed into compacts inside a rotating field to ensure magnetization in plane. Samples then underwent VSM, XRD, and scanning electron microscopy to determine the orientation effect. In addition, the complex permittivity and permeability of these samples were measured as a function of applied field and processing conditions. The results show strong orientation in these compacts making them practical for a variety of device applications.
In recent years, multifunctional materials contained simultaneous ferroelectric and ferromagnetic... more In recent years, multifunctional materials contained simultaneous ferroelectric and ferromagnetic ordering have been realized. Here, a real time room temperature adaptive materials system, which demonstrates an RF magnetodielectric (MD) response, i.e., CexY3-xFe5O12 (x = 0, 0.05, 0.1, 0.15, 0.2), is reported. The magnetic and dielectric properties of Ce-doped YIG microwave ferrites processed by a traditional ceramic route have been measured over a frequency range of 4-8 GHz (C-band). The substitution of Ce not only enhances the microwave electromagnetic properties of the YIG, but also modulates the magnetodielectric response. The maximum magnetodielectric response in Ce-doped YIG sample ranges in magnitude from approximately +5% to -5% under an applied field of 1.78 kOe. This effect was attributed to electron fluctuations on the Fe cation sites. Furthermore, the magnitude of the MD response was shown to be enhanced by the cerium content. It is believed that research of the magnetodi...
A nanoscale-driven crystal growth of magnetic hexaferrites was successfully demonstrated at low g... more A nanoscale-driven crystal growth of magnetic hexaferrites was successfully demonstrated at low growth temperatures (25-40% lower than the temperatures required often for crystal growth). This outcome exhibits thermodynamic processes of crystal growth, allowing ease in fabrication of advanced multifunctional materials. Most importantly, the crystal growth technique is considered theoretically and experimentally to be universal and suitable for the growth of a wide range of diverse crystals. In the present experiment, the conical spin structure of Co2Y ferrite crystals was found to give rise to an intrinsic magnetoelectric effect. Our experiment reveals a remarkable increase in the conical phase transition temperature by ∼150 K for Co2Y ferrite, compared to 5-10 K of Zn2Y ferrites recently reported. The high quality Co2Y ferrite crystals, having low microwave loss and magnetoelectricity, were successfully grown on a wide bandgap semiconductor GaN. The demonstration of the nanostructu...
Cobalt carbide magnetic nanoparticles were successfully synthesized via a modified polyol process... more Cobalt carbide magnetic nanoparticles were successfully synthesized via a modified polyol process without using a rare-earth catalyst during the synthesis process. The present results show admixtures of Co 2 C and Co 3 C phases possessing magnetization values exceeding 47 emu/g and coercivity values exceeding 2.3 kOe at room temperature. Moreover, these experiments have illuminated the important role of the reaction temperature, hydroxyl ion concentrations and the reaction duration on the crystallographic structure and magnetic properties of the nanoparticles. The crystallographic structure and particle size of the Co x C nanoparticles were characterized by Xray diffractometry and scanning electron microscopy. Vibrating sample magnetometry was used to determine magnetic properties. Scale-up of synthesis to more than 5 grams per batch was demonstrated with no significant degradation of magnetic properties.
Mn ferrite (MnFe 2 O 4) nanoparticles, having diameters from 4 to 50 nm, were synthesized using a... more Mn ferrite (MnFe 2 O 4) nanoparticles, having diameters from 4 to 50 nm, were synthesized using a modified co-precipitation technique in which mixed metal chloride solutions were added to different concentrations of boiling NaOH solutions to control particle growth rate. Thermomagnetization measurements indicated an increase in Néel temperature corresponding to increased particle growth rate and particle size. The Néel temperature is also found to increase inversely proportionally to the cation inversion parameter, δ, appearing in the formula (Mn 1−δ Fe δ) tet [Mn δ Fe 2−δ ] oct O 4. These results contradict previously published reports of trends between Néel temperature and particle size, and demonstrate the dominance of cation inversion in determining the strength of superexchange interactions and subsequently Néel temperature in ferrite systems. The particle surface chemistry, structure, and magnetic spin configuration play secondary roles.
Microwave magnetoelectric coupling in a ferroelectric/ferromagnetic/semiconductor multiferroic (M... more Microwave magnetoelectric coupling in a ferroelectric/ferromagnetic/semiconductor multiferroic (MF) heterostructure, consisting of a Co2MnAl epitaxial film grown on a GaAs substrate bonded to a lead magnesium niobate–lead titanate (PMN-PT) crystal, is reported. Ferromagnetic resonance measurements were carried out at X-band under the application of electric fields. Results indicate a frequency tuning of 125 MHz for electric field strength of 8 kV cm−1 resulting in a magnetoelectric coupling coefficient of 3.4 Oe cm kV−1. This work explores the potential of electronically controlled MF devices for use in future monolithic microwave integrated circuits.
Co 2 Z hexaferrite materials possess intrinsically high permeability, zero field ferromagnetic re... more Co 2 Z hexaferrite materials possess intrinsically high permeability, zero field ferromagnetic resonance values ($ 1 GHz), and have their magnetic orientation in the plane perpendicular to the c-axis. These characteristics make these materials practical for applications in low to mid ultra-high frequency and L-band microwave device designs. Due to the relatively large size of elements operating within these bands, it has become important to produce large amounts of Co 2 Z type hexaferrite materials. A modified co-precipitation method has been proposed to produce scalable quantities of high quality Co 2 Z hexaferrite particles, at $ 24 g/L. These particles have been thoroughly characterized by vibrating sample magnetometry (VSM) and X-ray diffraction (XRD) with regard to phase purity and magnetic properties. After formation and subsequent ball milling, to achieve single domain particles on the order of 0.5-2 um, particles were oriented and pressed into compacts inside a rotating field to ensure magnetization in plane. Samples then underwent VSM, XRD, and scanning electron microscopy to determine the orientation effect. In addition, the complex permittivity and permeability of these samples were measured as a function of applied field and processing conditions. The results show strong orientation in these compacts making them practical for a variety of device applications.
Films consisting of Zn1−xFexO were prepared by alternating-target laser ablation deposition. The ... more Films consisting of Zn1−xFexO were prepared by alternating-target laser ablation deposition. The Fe doping levels ranged from x=0.016to0.125at.%. X-ray diffraction and energy dispersive x-ray spectroscopy measurements showed only (002n) reflections of the ZnO host and confirmation of the Fe concentration, respectively. For films grown on (001) Al2O3 at 300K, room temperature average saturation magnetization, ⟨4πMs⟩, measured from superconducting quantum interference device (SQUID) hysteresis loops for x=0.125±0.025 was 172G. Although SQUID measurements were sensitive to the average value of the saturation magnetization, ferrimagnetic resonance measurements appeared to be sensitive only to the saturation magnetization of the so-called magnetic layer containing ferric ions. We believe that we have produced a host semiconductor material doped with impurities of ferrimagnetic ordering.
Varying amounts of boron were added to the host FeGa alloy to investigate its impact upon local a... more Varying amounts of boron were added to the host FeGa alloy to investigate its impact upon local atomic structure and magnetic and microwave properties. The impact of B upon the local atomic structure in FeGaB films was investigated by extended x-ray absorption fine structure (EXAFS) analysis. The EXAFS fitting results revealed a contraction of lattice parameters with the introduction of B. The Debye–Waller factor determined from EXAFS fitting increases as a function of boron addition and abruptly changes during the structural evolution from crystalline to amorphous that occurs near 9% B. Upon the onset of this transition the static and microwave magnetic properties became exceptionally soft, with values of coercivity and ferromagnetic linewidth reducing to less than 1 Oe and 25 Oe, respectively.
We demonstrate a significant control of the polarization response under an applied magnetic field... more We demonstrate a significant control of the polarization response under an applied magnetic field for a magnetoelectric (ME) heterostructure. This structure was comprised of a 2 μm thick ferroelectric BaTiO3 (BTO) film deposited on flexible ferromagnetic metallic glass foil (25 μm thick). Au was used as a buffer layer to control BTO growth orientation, and to protect the metallic glass from oxidation. x-ray diffraction and scanning electron microscopy demonstrated the successful growth of well-crystallized BTO films with a high degree of (111) orientation on the amorphous metallic glass foils. Well-defined polarization (P-E) and magnetization (M-H) hysteresis loops confirmed the coexistence of ferroelectric and ferromagnetic properties. A ME voltage coefficient of about ∼60 mV/cm Oe was measured.
We design a multiferroic laminated heterostructure composed of a Fe-Ga magnetostrictive layer and... more We design a multiferroic laminated heterostructure composed of a Fe-Ga magnetostrictive layer and a PMN-PT piezoelectric layer and examine the converse magnetoelectric effect (CME). Such a heterostructure is potentially useful as a magnetic field generator, which can be used in the tuning of microwave devices. Magnetization, magnetic coercivity, remanence, and squareness exhibit pronounced hysteretic behavior and potential for tuning with an applied electric field. We obtain E = 12:5 Oe cm kV 01. The deformation of the PMN-PT under an applied electric field results in an internal stress-induced magnetic field, with an experimentally determined value of 100 Oe. The tunable range of fringe fields generated by the stress-induced field is predicted to be 104 Oe. The results will establish a foundation in the design of E-field tunable magnetic devices.
In the present work, exchange coupled and non-exchange coupled BaFe 12 O 19 (BaM)/NiFe 2 O 4 (NiF... more In the present work, exchange coupled and non-exchange coupled BaFe 12 O 19 (BaM)/NiFe 2 O 4 (NiF) nanocomposites with varying composition were prepared by adopting two different processing methods. Phase formation and microstructural changes were analyzed by X-ray diffraction (XRD) and Scanning electron microscopy (SEM) respectively. Effect of exchange coupling on magnetic and microwave properties (in Ku-band) were studied by vibrating sample magnetometer and vector network analyser respectively. XRD patterns confirmed the coexistence of BaM and NiF phases in composites without any secondary phase. SEM micrographs showed the well distinguished BaM and NiF grains in exchange coupled composites. Smooth hysteresis loops were observed for exchange coupled composites in contrast to non-exchanged coupled, which showed stepped-loops for all studied compositions. Higher saturation magnetization (M s) was also found in exchange coupled composites. Whereas, M s showed a linear decrease with NiF content in non-coupled composites. Coercivity found to decrease with NiF content with distinct trend among the two systems. Frequency dependent complex permittivity and permeability showed large variation between the two systems. Reflection losses at multiple frequencies were observed in exchange coupled composites.
ABSTRACT The deposition and characterization of high quality ferrite thin films by the alternatin... more ABSTRACT The deposition and characterization of high quality ferrite thin films by the alternating target laser ablation deposition (ATLAD) technique is discussed with the emphasis on the unique magnetic properties induced in these materials by stabilizing far from equilibrium cation distributions. Two spinel systems and three hexagonal ferrite systems are studied. In the case of manganese spinel ferrite a large in-plane uniaxial anisotropy field ( > 5 kOe) is induced in ATLAD deposited films. In the case of copper spinel ferrite a 65% enhancement in the saturation magnetization is observed over the bulk value. In the case of manganese substituted barium ferrite a 12-22% enhancement in low temperature saturation magnetization and 40-60 K increase in the Neel temperature is observed. The unique magnetic properties of the films are correlated with the cation distributions stabilized by the application of the ATLAD technique as determined by the extended X-ray absorption fine structure (EXAFS) analysis.
IEEE Microwave and Wireless Components Letters, 2011
... u Band Jianwei Wang, Aria Yang, Yajie Chen, Zhaohui Chen, Anton Geiler, Scott M. Gillette, Vi... more ... u Band Jianwei Wang, Aria Yang, Yajie Chen, Zhaohui Chen, Anton Geiler, Scott M. Gillette, Vincent G. Harris, and ... and where is the remnant magnetization, is the uniaxial mag-netocrystalline anisotropy field, is the radial frequency, and is the electron gyromagnetic ratio. ...
A miniature, quasi one dimensional, magnetic field sensor based on magnetoelectric coupling is pr... more A miniature, quasi one dimensional, magnetic field sensor based on magnetoelectric coupling is presented. The magnetoelectric sensor makes use of the d31 coupling mode between a piezoelectric lead zirconate titanate tube and FeNi magnetostrictive wire. The sensors demonstrate high sensitivity, high signal-to-noise ratio, and low noise floor at zero DC magnetic bias field and at low frequency resulting in smaller, lower power consumption, and volumetric efficiency. Experiments indicate a zero bias field sensitivity of 16.5 mV/Oe at 100 Hz stemming from a magnetoelectric coefficient of 1.65 V/cm-Oe. The results are quantitatively described by a theoretical model of laminate composites.
We design a multiferroic laminated heterostructure composed of a Fe-Ga magnetostrictive layer and... more We design a multiferroic laminated heterostructure composed of a Fe-Ga magnetostrictive layer and a PMN-PT piezoelectric layer and examine the converse magnetoelectric effect (CME). Such a heterostructure is potentially useful as a magnetic field generator, which can be used in the tuning of microwave devices. Magnetization, magnetic coercivity, remanence, and squareness exhibit pronounced hysteretic behavior and potential for tuning with an applied electric field. We obtain E = 12:5 Oe cm kV 01. The deformation of the PMN-PT under an applied electric field results in an internal stress-induced magnetic field, with an experimentally determined value of 100 Oe. The tunable range of fringe fields generated by the stress-induced field is predicted to be 104 Oe. The results will establish a foundation in the design of E-field tunable magnetic devices.
Journal of Magnetism and Magnetic Materials, Nov 1, 2012
Co 2 Z hexaferrite materials possess intrinsically high permeability, zero field ferromagnetic re... more Co 2 Z hexaferrite materials possess intrinsically high permeability, zero field ferromagnetic resonance values ($ 1 GHz), and have their magnetic orientation in the plane perpendicular to the c-axis. These characteristics make these materials practical for applications in low to mid ultra-high frequency and L-band microwave device designs. Due to the relatively large size of elements operating within these bands, it has become important to produce large amounts of Co 2 Z type hexaferrite materials. A modified co-precipitation method has been proposed to produce scalable quantities of high quality Co 2 Z hexaferrite particles, at $ 24 g/L. These particles have been thoroughly characterized by vibrating sample magnetometry (VSM) and X-ray diffraction (XRD) with regard to phase purity and magnetic properties. After formation and subsequent ball milling, to achieve single domain particles on the order of 0.5-2 um, particles were oriented and pressed into compacts inside a rotating field to ensure magnetization in plane. Samples then underwent VSM, XRD, and scanning electron microscopy to determine the orientation effect. In addition, the complex permittivity and permeability of these samples were measured as a function of applied field and processing conditions. The results show strong orientation in these compacts making them practical for a variety of device applications.
In recent years, multifunctional materials contained simultaneous ferroelectric and ferromagnetic... more In recent years, multifunctional materials contained simultaneous ferroelectric and ferromagnetic ordering have been realized. Here, a real time room temperature adaptive materials system, which demonstrates an RF magnetodielectric (MD) response, i.e., CexY3-xFe5O12 (x = 0, 0.05, 0.1, 0.15, 0.2), is reported. The magnetic and dielectric properties of Ce-doped YIG microwave ferrites processed by a traditional ceramic route have been measured over a frequency range of 4-8 GHz (C-band). The substitution of Ce not only enhances the microwave electromagnetic properties of the YIG, but also modulates the magnetodielectric response. The maximum magnetodielectric response in Ce-doped YIG sample ranges in magnitude from approximately +5% to -5% under an applied field of 1.78 kOe. This effect was attributed to electron fluctuations on the Fe cation sites. Furthermore, the magnitude of the MD response was shown to be enhanced by the cerium content. It is believed that research of the magnetodi...
A nanoscale-driven crystal growth of magnetic hexaferrites was successfully demonstrated at low g... more A nanoscale-driven crystal growth of magnetic hexaferrites was successfully demonstrated at low growth temperatures (25-40% lower than the temperatures required often for crystal growth). This outcome exhibits thermodynamic processes of crystal growth, allowing ease in fabrication of advanced multifunctional materials. Most importantly, the crystal growth technique is considered theoretically and experimentally to be universal and suitable for the growth of a wide range of diverse crystals. In the present experiment, the conical spin structure of Co2Y ferrite crystals was found to give rise to an intrinsic magnetoelectric effect. Our experiment reveals a remarkable increase in the conical phase transition temperature by ∼150 K for Co2Y ferrite, compared to 5-10 K of Zn2Y ferrites recently reported. The high quality Co2Y ferrite crystals, having low microwave loss and magnetoelectricity, were successfully grown on a wide bandgap semiconductor GaN. The demonstration of the nanostructu...
Cobalt carbide magnetic nanoparticles were successfully synthesized via a modified polyol process... more Cobalt carbide magnetic nanoparticles were successfully synthesized via a modified polyol process without using a rare-earth catalyst during the synthesis process. The present results show admixtures of Co 2 C and Co 3 C phases possessing magnetization values exceeding 47 emu/g and coercivity values exceeding 2.3 kOe at room temperature. Moreover, these experiments have illuminated the important role of the reaction temperature, hydroxyl ion concentrations and the reaction duration on the crystallographic structure and magnetic properties of the nanoparticles. The crystallographic structure and particle size of the Co x C nanoparticles were characterized by Xray diffractometry and scanning electron microscopy. Vibrating sample magnetometry was used to determine magnetic properties. Scale-up of synthesis to more than 5 grams per batch was demonstrated with no significant degradation of magnetic properties.
Mn ferrite (MnFe 2 O 4) nanoparticles, having diameters from 4 to 50 nm, were synthesized using a... more Mn ferrite (MnFe 2 O 4) nanoparticles, having diameters from 4 to 50 nm, were synthesized using a modified co-precipitation technique in which mixed metal chloride solutions were added to different concentrations of boiling NaOH solutions to control particle growth rate. Thermomagnetization measurements indicated an increase in Néel temperature corresponding to increased particle growth rate and particle size. The Néel temperature is also found to increase inversely proportionally to the cation inversion parameter, δ, appearing in the formula (Mn 1−δ Fe δ) tet [Mn δ Fe 2−δ ] oct O 4. These results contradict previously published reports of trends between Néel temperature and particle size, and demonstrate the dominance of cation inversion in determining the strength of superexchange interactions and subsequently Néel temperature in ferrite systems. The particle surface chemistry, structure, and magnetic spin configuration play secondary roles.
Microwave magnetoelectric coupling in a ferroelectric/ferromagnetic/semiconductor multiferroic (M... more Microwave magnetoelectric coupling in a ferroelectric/ferromagnetic/semiconductor multiferroic (MF) heterostructure, consisting of a Co2MnAl epitaxial film grown on a GaAs substrate bonded to a lead magnesium niobate–lead titanate (PMN-PT) crystal, is reported. Ferromagnetic resonance measurements were carried out at X-band under the application of electric fields. Results indicate a frequency tuning of 125 MHz for electric field strength of 8 kV cm−1 resulting in a magnetoelectric coupling coefficient of 3.4 Oe cm kV−1. This work explores the potential of electronically controlled MF devices for use in future monolithic microwave integrated circuits.
Co 2 Z hexaferrite materials possess intrinsically high permeability, zero field ferromagnetic re... more Co 2 Z hexaferrite materials possess intrinsically high permeability, zero field ferromagnetic resonance values ($ 1 GHz), and have their magnetic orientation in the plane perpendicular to the c-axis. These characteristics make these materials practical for applications in low to mid ultra-high frequency and L-band microwave device designs. Due to the relatively large size of elements operating within these bands, it has become important to produce large amounts of Co 2 Z type hexaferrite materials. A modified co-precipitation method has been proposed to produce scalable quantities of high quality Co 2 Z hexaferrite particles, at $ 24 g/L. These particles have been thoroughly characterized by vibrating sample magnetometry (VSM) and X-ray diffraction (XRD) with regard to phase purity and magnetic properties. After formation and subsequent ball milling, to achieve single domain particles on the order of 0.5-2 um, particles were oriented and pressed into compacts inside a rotating field to ensure magnetization in plane. Samples then underwent VSM, XRD, and scanning electron microscopy to determine the orientation effect. In addition, the complex permittivity and permeability of these samples were measured as a function of applied field and processing conditions. The results show strong orientation in these compacts making them practical for a variety of device applications.
Films consisting of Zn1−xFexO were prepared by alternating-target laser ablation deposition. The ... more Films consisting of Zn1−xFexO were prepared by alternating-target laser ablation deposition. The Fe doping levels ranged from x=0.016to0.125at.%. X-ray diffraction and energy dispersive x-ray spectroscopy measurements showed only (002n) reflections of the ZnO host and confirmation of the Fe concentration, respectively. For films grown on (001) Al2O3 at 300K, room temperature average saturation magnetization, ⟨4πMs⟩, measured from superconducting quantum interference device (SQUID) hysteresis loops for x=0.125±0.025 was 172G. Although SQUID measurements were sensitive to the average value of the saturation magnetization, ferrimagnetic resonance measurements appeared to be sensitive only to the saturation magnetization of the so-called magnetic layer containing ferric ions. We believe that we have produced a host semiconductor material doped with impurities of ferrimagnetic ordering.
Varying amounts of boron were added to the host FeGa alloy to investigate its impact upon local a... more Varying amounts of boron were added to the host FeGa alloy to investigate its impact upon local atomic structure and magnetic and microwave properties. The impact of B upon the local atomic structure in FeGaB films was investigated by extended x-ray absorption fine structure (EXAFS) analysis. The EXAFS fitting results revealed a contraction of lattice parameters with the introduction of B. The Debye–Waller factor determined from EXAFS fitting increases as a function of boron addition and abruptly changes during the structural evolution from crystalline to amorphous that occurs near 9% B. Upon the onset of this transition the static and microwave magnetic properties became exceptionally soft, with values of coercivity and ferromagnetic linewidth reducing to less than 1 Oe and 25 Oe, respectively.
We demonstrate a significant control of the polarization response under an applied magnetic field... more We demonstrate a significant control of the polarization response under an applied magnetic field for a magnetoelectric (ME) heterostructure. This structure was comprised of a 2 μm thick ferroelectric BaTiO3 (BTO) film deposited on flexible ferromagnetic metallic glass foil (25 μm thick). Au was used as a buffer layer to control BTO growth orientation, and to protect the metallic glass from oxidation. x-ray diffraction and scanning electron microscopy demonstrated the successful growth of well-crystallized BTO films with a high degree of (111) orientation on the amorphous metallic glass foils. Well-defined polarization (P-E) and magnetization (M-H) hysteresis loops confirmed the coexistence of ferroelectric and ferromagnetic properties. A ME voltage coefficient of about ∼60 mV/cm Oe was measured.
We design a multiferroic laminated heterostructure composed of a Fe-Ga magnetostrictive layer and... more We design a multiferroic laminated heterostructure composed of a Fe-Ga magnetostrictive layer and a PMN-PT piezoelectric layer and examine the converse magnetoelectric effect (CME). Such a heterostructure is potentially useful as a magnetic field generator, which can be used in the tuning of microwave devices. Magnetization, magnetic coercivity, remanence, and squareness exhibit pronounced hysteretic behavior and potential for tuning with an applied electric field. We obtain E = 12:5 Oe cm kV 01. The deformation of the PMN-PT under an applied electric field results in an internal stress-induced magnetic field, with an experimentally determined value of 100 Oe. The tunable range of fringe fields generated by the stress-induced field is predicted to be 104 Oe. The results will establish a foundation in the design of E-field tunable magnetic devices.
In the present work, exchange coupled and non-exchange coupled BaFe 12 O 19 (BaM)/NiFe 2 O 4 (NiF... more In the present work, exchange coupled and non-exchange coupled BaFe 12 O 19 (BaM)/NiFe 2 O 4 (NiF) nanocomposites with varying composition were prepared by adopting two different processing methods. Phase formation and microstructural changes were analyzed by X-ray diffraction (XRD) and Scanning electron microscopy (SEM) respectively. Effect of exchange coupling on magnetic and microwave properties (in Ku-band) were studied by vibrating sample magnetometer and vector network analyser respectively. XRD patterns confirmed the coexistence of BaM and NiF phases in composites without any secondary phase. SEM micrographs showed the well distinguished BaM and NiF grains in exchange coupled composites. Smooth hysteresis loops were observed for exchange coupled composites in contrast to non-exchanged coupled, which showed stepped-loops for all studied compositions. Higher saturation magnetization (M s) was also found in exchange coupled composites. Whereas, M s showed a linear decrease with NiF content in non-coupled composites. Coercivity found to decrease with NiF content with distinct trend among the two systems. Frequency dependent complex permittivity and permeability showed large variation between the two systems. Reflection losses at multiple frequencies were observed in exchange coupled composites.
ABSTRACT The deposition and characterization of high quality ferrite thin films by the alternatin... more ABSTRACT The deposition and characterization of high quality ferrite thin films by the alternating target laser ablation deposition (ATLAD) technique is discussed with the emphasis on the unique magnetic properties induced in these materials by stabilizing far from equilibrium cation distributions. Two spinel systems and three hexagonal ferrite systems are studied. In the case of manganese spinel ferrite a large in-plane uniaxial anisotropy field ( > 5 kOe) is induced in ATLAD deposited films. In the case of copper spinel ferrite a 65% enhancement in the saturation magnetization is observed over the bulk value. In the case of manganese substituted barium ferrite a 12-22% enhancement in low temperature saturation magnetization and 40-60 K increase in the Neel temperature is observed. The unique magnetic properties of the films are correlated with the cation distributions stabilized by the application of the ATLAD technique as determined by the extended X-ray absorption fine structure (EXAFS) analysis.
IEEE Microwave and Wireless Components Letters, 2011
... u Band Jianwei Wang, Aria Yang, Yajie Chen, Zhaohui Chen, Anton Geiler, Scott M. Gillette, Vi... more ... u Band Jianwei Wang, Aria Yang, Yajie Chen, Zhaohui Chen, Anton Geiler, Scott M. Gillette, Vincent G. Harris, and ... and where is the remnant magnetization, is the uniaxial mag-netocrystalline anisotropy field, is the radial frequency, and is the electron gyromagnetic ratio. ...
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