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Articles 1 - 30 of 67
Full-Text Articles in Physics
Effect Of Disorder On Quantum Phase Transition In The Double Layered Ruthenates (Sr1−Xcax)3ru2o7effect Of Disorder On Quantum Phase Transition In The Double Layered Ruthenates (Sr1−Xcax)3ru2o7, Leonard Spinu, Zhe Qu, Jin Peng, Tijang Liu, David Forbes, Vkad Dobrosavljevic, Z Q. Mao
Effect Of Disorder On Quantum Phase Transition In The Double Layered Ruthenates (Sr1−Xcax)3ru2o7effect Of Disorder On Quantum Phase Transition In The Double Layered Ruthenates (Sr1−Xcax)3ru2o7, Leonard Spinu, Zhe Qu, Jin Peng, Tijang Liu, David Forbes, Vkad Dobrosavljevic, Z Q. Mao
Physics Faculty Publications
(Sr1−xCax)3Ru2O7 is characterized by complex magnetic states, spanning from a long-range antiferromagnetically ordered state over an unusual heavy-mass nearly ferromagnetic (NFM) state to an itinerant metamagnetic (IMM) state. The NFM state, which occurs in the 0.4 > x > 0.08 composition range, freezes into a clusterspin glass (CSG) phase at low temperatures [Z. Qu et al., Phys. Rev. B 78, 180407(R) (2008)]. In this article, we present the scaling analyses of magnetization and the specific heat for (Sr1−xCax)3Ru2O7 in the 0.4 > x > 0.08 composition …
Electric Field Tunable Magnetic Properties Of Lead-Free Na0.5bi0.5tio3/Cofe2o4 Multiferroic Composites, S Narendra Babu, Seong Gi Min, Leszek Malkinski
Electric Field Tunable Magnetic Properties Of Lead-Free Na0.5bi0.5tio3/Cofe2o4 Multiferroic Composites, S Narendra Babu, Seong Gi Min, Leszek Malkinski
Physics Faculty Publications
Lead-free multiferroic particulate composites of Na0.5Bi0.5TiO3 (NBT) and CoFe2O4 (CFO) have been synthesized by solid-state sintering method. A systematic study of structural, magnetic and magnetoelectric (ME) properties is undertaken. Structural and morphology studies carried out by x-ray diffraction and field emission scanning electron microscopy indicate formation of single phase for parent phases and presence of both phases in the composites. Magnetic properties are investigated using vibrating sample magnetometer and ferromagnetic resonance (FMR) measurements at room temperature. Strong ME coupling is demonstrated in NBT-CFO 70-30 mol% composite by an electrostatically tunable FMR field …
Calorimetric Evidence Of Strong-Coupling Multiband Superconductivity In Fe(Te0.57se0.43) Single Crystal, J. Hu, T. J. Liu, B. Qian, A. Rotaru, L. Spinu, Z. Q. Mao
Calorimetric Evidence Of Strong-Coupling Multiband Superconductivity In Fe(Te0.57se0.43) Single Crystal, J. Hu, T. J. Liu, B. Qian, A. Rotaru, L. Spinu, Z. Q. Mao
Physics Faculty Publications
We have investigated the specific heat of optimally doped iron chalcogenide superconductor Fe(Te0.57Se0.43) with a high-quality single crystal sample. The electronic specific heat Ce of this sample has been successfully separated from the phonon contribution using the specific heat of a nonsuperconducting sample (Fe0.90Cu0.10)(Te0.57Se0.43) as a reference. The normal-state Sommerfeld coefficient γn of the superconducting sample is found to be ~26.6 mJ/mol K2, indicating intermediate electronic correlation. The temperature dependence of Ce in the superconducting state can be best fitted using a double-gap …
Thermally Activated Transitions In A System Of Two Single Domain Ferromagnetic Particles, Dorin Cimpoesu, Alexandru Stancu, Ivo Kilk, Ching-Ray Chang, Leonard Spinu
Thermally Activated Transitions In A System Of Two Single Domain Ferromagnetic Particles, Dorin Cimpoesu, Alexandru Stancu, Ivo Kilk, Ching-Ray Chang, Leonard Spinu
Physics Faculty Publications
Numerical simulations based on the stochastic Langevin equation are applied here to a system of two uniaxial single domain ferromagnetic particles with antiferromagnetic dipolar coupling. The hysteresis loops of a strongly coupled systems exhibit fully demagnetized, intermediate metastable configurations which separate the two fully saturated states. At small magnetostatic couplings, on the other hand, and at sufficiently weak damping, the intermediate metastable configuration becomes only partially demagnetized. This state cannot be associated with any single local minimum of the free energy function.
Synthesis Of Mild–Hard Aao Templates For Studying Magnetic Interactions Between Metal Nanowires, Jin-Hee Lim, Aurelian Rotaru, Seong-Gi Min, Leszek Malkinski, John B. Wiley
Synthesis Of Mild–Hard Aao Templates For Studying Magnetic Interactions Between Metal Nanowires, Jin-Hee Lim, Aurelian Rotaru, Seong-Gi Min, Leszek Malkinski, John B. Wiley
Physics Faculty Publications
The sequential application of mild and hard anodization techniques in the fabrication of porous aluminamembranes allows one to decrease the number of continuous pores in anodized aluminium oxide (AAO) templates. Initially, standard mild anodization techniques were used to create porous templates with 100 nm interpore distances and 70 nm pore diameters. Hard anodization treatment on the same membrane then produced interpore distances of about 265 nm with diameters of 110 nm. At the interface between the two anodization steps, many of the mild-side pores were terminated to create a mild–hard membrane (Mi–Ha AAO) where the functional interpore distances were 200–300 …
Interplay Between The Lattice And Spin Degrees Of Freedom In (Sr1−Xcax)3ru2o7, Jin Peng, David Fobes, Tijian Liu, Xiaoshan Wu, H M. Pham, Leonard Spinu, Z Q. Mao
Interplay Between The Lattice And Spin Degrees Of Freedom In (Sr1−Xcax)3ru2o7, Jin Peng, David Fobes, Tijian Liu, Xiaoshan Wu, H M. Pham, Leonard Spinu, Z Q. Mao
Physics Faculty Publications
The Sr1−xCax3Ru2O7 solid solution series exhibits complex magnetic ground states, ranging from an itinerant metamagnetic state, to a quasi-two-dimensional 2D heavy-mass nearly ferromagneticFM state, and finally to a long-range antiferromagnetically ordered state Z. Qu et al. Phys. Rev. B. 78, R180407 2008. In this paper, we investigate the evolution of structural distortion and magnetic anisotropy with Ca content in this material system. Our results show that both the magnetic phase transitions and magnetic anistropy of this system couple with the evolution of structure distortion. The transformation from the itinerant metamagnetic to the nearly ferromagnetic state is accompanied …
Fabrication And Magnetic Properties Of Fe Nanostructures In Anodic Alumina Membrane, J H. Lim, W S. Chae, H O. Lee, L Malkinski, S G. Min, J B. Wiley, J H. Jun, S H. Lee, J S. Jung
Fabrication And Magnetic Properties Of Fe Nanostructures In Anodic Alumina Membrane, J H. Lim, W S. Chae, H O. Lee, L Malkinski, S G. Min, J B. Wiley, J H. Jun, S H. Lee, J S. Jung
Physics Faculty Publications
Several Fe nanostructures with different lengths, diameters, and separations of the constituting magnetic components have been synthesized using anodized alumina membranes (AAMs) to understand the influence of these parameters on their magnetic properties. Fe nanostructures with high crystallinity and (110) orientation were synthesized by electrodeposition at room temperature in regular AAMs and mild-hard AAM (Mi-Ha AAM). Fe nanostructures with different aspect ratios (1:1, 1:10, and 1:75) in the form of nanodots, nanorods, or nanowires were synthesized in regular AAMs with the 100 nm interpore distance. Mi-Ha AAMs with two different pore sizes (70 and 120 nm) and 250 nm interpore …
Collinear Phase Matching For Second Harmonic Generation Using Conoscopic Interferometry, A Puri, A De
Collinear Phase Matching For Second Harmonic Generation Using Conoscopic Interferometry, A Puri, A De
Physics Faculty Publications
The problem of finding phase-matching directions in noncentrosymmetric biaxial crystals is simplified here by the use of Conoscopic interferometry. Based on vector relations for wave propagation in birefringent media and solutions to phase-matching equations, we show that phase matching directions can be located on the conoscopic interferograms and that fringe numbers for dark-isochromes can be used as a guide to find phase-matching directions for a biaxial crystal. This technique can be generalized and extended to any anisotropic crystal. We have demonstrated this method for the particular case of a biaxial KTiOPO4 crystal, where it is found to be particularly …
Complex Electronic States In Double-Layered Ruthenates (Sr1−Xcax)3ru2o7, Zhe Qu, Jin Peng, David Fobes, Leonard Spinu, Zhiqiang Mao
Complex Electronic States In Double-Layered Ruthenates (Sr1−Xcax)3ru2o7, Zhe Qu, Jin Peng, David Fobes, Leonard Spinu, Zhiqiang Mao
Physics Faculty Publications
The magnetic ground state of (Sr1−xCax)3Ru2O7 (0≤x≤1) is complex, ranging from an itinerant metamagnetic state (0≤x<0.08) to an unusual heavy-mass nearly ferromagnetic (FM) state (0.08<x<0.4), and finally to an antiferromagnetic (AFM) state (0.4≤x≤1). In this report we elucidate the electronic properties for these magnetic states, and show that the electronic and magnetic properties are strongly coupled in this system. The electronic ground state evolves from an AFM quasi-two-dimensional metal for x=1.0 to an Anderson localized state for 0.4≤x<1.0 (the AFM region). When the magnetic state undergoes a transition from the AFM to the nearly FM state, the electronic ground state switches to a weakly localized state induced by magnetic scattering for 0.25≤x<0.4, and then to a magnetic metallic state with the in-plane resistivity ρab∝Tα (α>2) for 0.08<x<0.25. The system eventually transforms into a Fermi-liquid ground state when the magnetic ground state enters the itinerant metamagnetic state for x<0.08. When x approaches the critical composition (x∼0.08), …
Morphology, Magnetic And Dynamic Properties Of Artificial Structures Assembled By Acoustic Vibrations, K B. Paul, L Malkinski
Morphology, Magnetic And Dynamic Properties Of Artificial Structures Assembled By Acoustic Vibrations, K B. Paul, L Malkinski
Physics Faculty Publications
Cobalt micromagnetic particles with an average size of ≈ 1.6 μm and varying total mass of the powder were assembled on patterned media with perpendicular magnetization by acoustic vibrations onto designed shapes reflecting the primary material. The replicas were studied with scanning electron microscopy, vibrating sample magnetometry, and ferromagnetic resonance spectroscopy. Their properties were significantly influenced by the shape anisotropy induced through the parent molds. A tendency in the development of the physical characteristics of the replicas was observed as their geometrical parameters changed.
Charge-Carrier Localization Induced By Excess Fe In The Superconductor Fe1+Yte1−Xsex, T J. Liu, X Ke, B Qian, J Hu, D Fobes, E K. Vehstedt, H Pham, J H. Yang, M H. Fang, L Spinu, P Schiffer, Y Liu, Z Q. Mao
Charge-Carrier Localization Induced By Excess Fe In The Superconductor Fe1+Yte1−Xsex, T J. Liu, X Ke, B Qian, J Hu, D Fobes, E K. Vehstedt, H Pham, J H. Yang, M H. Fang, L Spinu, P Schiffer, Y Liu, Z Q. Mao
Physics Faculty Publications
We have investigated the effect of Fe nonstoichiometry on properties of the Fe1+y(Te,Se) superconductor system by means of resistivity, Hall coefficient, magnetic susceptibility, and specific-heat measurements. We find that the excess Fe at interstitial sites of the (Te, Se) layers not only suppresses superconductivity but also results in a weakly localized electronic state. We argue that these effects originate from the magnetic coupling between the excess Fe and the adjacent Fe square-planar sheets, which favors a short-range magnetic order.
Dynamic Critical Curve Of A Synthetic Antiferromagnet, Huy Pham, Dorin Cimpoesu, Andrei-Valentin Plamada, Alexandru Stancu, Leonard Spinu
Dynamic Critical Curve Of A Synthetic Antiferromagnet, Huy Pham, Dorin Cimpoesu, Andrei-Valentin Plamada, Alexandru Stancu, Leonard Spinu
Physics Faculty Publications
We have investigated the effect of Fe nonstoichiometry on properties of the Fe1+y(Te,Se) superconductor system by means of resistivity, Hall coefficient, magnetic susceptibility, and specific-heat measurements. We find that the excess Fe at interstitial sites of the (Te, Se) layers not only suppresses superconductivity but also results in a weakly localized electronic state. We argue that these effects originate from the magnetic coupling between the excess Fe and the adjacent Fe square-planar sheets, which favors a short-range magnetic order.
Friction On The Microscale, K B. Paul, L Malkinski
Friction On The Microscale, K B. Paul, L Malkinski
Physics Faculty Publications
A new method is presented for measurements of friction of microsized particles on surfaces. Specifically in this work, the particles are alumina with diameters between ≈ 1 and 50 μm and the surfaces are InP, Si, and Cr. Friction is analyzed, its components are determined, and the friction coefficients are estimated from the experimental results. The technique and the specific instrument allow measurements of coefficients of friction for spherical particles with radii as small as 1 μm. For smaller sizes, the instrument needs to be modified by using a more powerful power supply, actuator with extended frequency and …
Structural, Magnetic, And Electronic Transport Properties Of (Sr0.9ca0.1)3ru2o7 Single Crystal, Bin Qian, Zhe Qu, Jin Peng, Tijang Liu, Xiaoshan Wu, L Spinu, Z Q. Mao
Structural, Magnetic, And Electronic Transport Properties Of (Sr0.9ca0.1)3ru2o7 Single Crystal, Bin Qian, Zhe Qu, Jin Peng, Tijang Liu, Xiaoshan Wu, L Spinu, Z Q. Mao
Physics Faculty Publications
We have studied the structural, magnetic, and electronic transport properties of (Sr0.9Ca0.1)3Ru2O7 using single crystals grown by a floating-zone technique. The structure analysis by Rietveld refinements reveals that the Ca substitution for Sr intensifies the structure distortion; the rotation angle of the RuO6 octahedron increases. This structure change tunes magnetic and transport properties dramatically. The magnetic ground state switches from an itinerant metamagnetic state for Sr3Ru2O7 to a nearly ferromagnetic state for (Sr0.9Ca0.1)3Ru2O7. The Fermi …
Magnetic Entropy Change Of V Substituted Ni–Mn–Ga Heusler Alloy, S G. Min, L Malkinski, Y D. Zhang, S C. Yu, K W. Lee, Y C. Kim
Magnetic Entropy Change Of V Substituted Ni–Mn–Ga Heusler Alloy, S G. Min, L Malkinski, Y D. Zhang, S C. Yu, K W. Lee, Y C. Kim
Physics Faculty Publications
The magnetization behaviors have been analyzed for Ni54Mn21−xVxGa25 (x = 0,2,4) alloys which were prepared by conventional arc melting method in argon atmosphere. The Curie temperature TC was found to be 325, 300, and 265 K and the austenitic transition temperature TA on heating was found to be 315, 217, and 124 K for x = 0, 2, and 4, respectively. The magnetic characteristics were performed with a Quantum Design superconducting quantum interference device magnetometer in the field of up to 20 kOe. A large magnetic entropy change Δ …
Tunable (Δπ, Δπ)-Type Antiferromagnetic Order In Α-Fe(Te,Se) Superconductors, Wei Bao, Y Qiu, Q Huang, M A. Green, P Zajdel, M R. Fitzsimmons, M Zhernenkov, S Chang, M Fang, B Qian, Jinhu Yang, H M. Pham, L Spinu, Z Q. Mao
Tunable (Δπ, Δπ)-Type Antiferromagnetic Order In Α-Fe(Te,Se) Superconductors, Wei Bao, Y Qiu, Q Huang, M A. Green, P Zajdel, M R. Fitzsimmons, M Zhernenkov, S Chang, M Fang, B Qian, Jinhu Yang, H M. Pham, L Spinu, Z Q. Mao
Physics Faculty Publications
The new α-Fe(Te,Se) superconductors share the common iron building block and ferminology with the LaFeAsO and BaFe2As2 families of superconductors. In contrast with the predicted commensurate spin-density-wave order at the nesting wave vector (π, 0), a completely different magnetic order with a composition tunable propagation vector (δπ, δπ) was determined for the parent compound Fe1+yTe in this powder and single-crystal neutron diffraction study. The new antiferromagnetic order survives as a short-range one even in the highest TC sample. An alternative to the prevailing nesting Fermi surface mechanism is required to understand the latest family …
Three-Dimensional Seismic Array Characterization Study: Experiment And Modeling, Arslan M. Tashmukhambetov, George E. Ioup, Juliette W. Ioup, Natalia A. Sidorovskaia, Joal J. Newcomb
Three-Dimensional Seismic Array Characterization Study: Experiment And Modeling, Arslan M. Tashmukhambetov, George E. Ioup, Juliette W. Ioup, Natalia A. Sidorovskaia, Joal J. Newcomb
Physics Faculty Publications
In the summer of 2003, the Littoral Acoustic Demonstration Center conducted an acoustic characterization experiment for a 21-element marine seismic exploration airgun array of total volume of 0.0588 m3 (3590 in.3). Two Environmental Acoustic Recording System buoys, one with a desensitized hydrophone, were deployed at a depth of 758 m in a water depth of 990 m, near Green’s Canyon in the Gulf of Mexico. Shots over a grid were recorded and calibrated to produce absolute broadband (up to 25 kHz) pressure-time dependencies for a wide range of offsets and arrival angles in the water column. Experimental …
Dynamic And Temperature Effects In Spin-Transfer Switching, Dorin Cimpoesu, Huy Pham, Leonard Spinu, Alexandru Stancu
Dynamic And Temperature Effects In Spin-Transfer Switching, Dorin Cimpoesu, Huy Pham, Leonard Spinu, Alexandru Stancu
Physics Faculty Publications
We have studied the dynamic switching triggered by spin angular momentum transfer in a pulsed current of a spin-valve-type trilayer structure, and its dependence on thermal effects. In order to determine the current pulse parameters, where fast and stable switching can be achieved, we have studied the magnetization’s dynamics properties as a function of applied current pulse amplitude and shape, waiting time, and initial orientation, and also as a function of the Gilbert damping constant. The magnetic layer is assumed to be single domain, ellipsoid shaped. In this paper also we present the thermal fluctuation effects on the switching behavior. …
Measurement Of The Critical Curve Of A Synthetic Antiferromagnet, Cosmin Radu, Dorin Cimpoesu, Alexandru Stancu, Leonard Spinu
Measurement Of The Critical Curve Of A Synthetic Antiferromagnet, Cosmin Radu, Dorin Cimpoesu, Alexandru Stancu, Leonard Spinu
Physics Faculty Publications
In this paper, we propose a method for a synthetic antiferromagnet structure’s critical curve determination. The method is based on reversible susceptibility’s singularities detection, as the magnetic field is swept along easy axis, in both positive and negative direction, while a hard axis bias field is also applied. By performing susceptibility measurements with different values of the bias field, the critical curve can be determined. Knowing the critical curve of a synthetic antiferromagnetic structure is essential for devices such as magnetic random access memories.
The Temperature Dependence Of Hysteretic Processes In Co Nanowires Arrays, I Astefanoaei, I Dumitru, A Diaconu, L Spinu, A Stancu
The Temperature Dependence Of Hysteretic Processes In Co Nanowires Arrays, I Astefanoaei, I Dumitru, A Diaconu, L Spinu, A Stancu
Physics Faculty Publications
In this paper, the temperature dependence of the hysteretic processes of Co nanowires, squarelly ordered in an array prepared by electrodeposition in nanopores of alumina membranes was analyzed. Both the magnetostatic interactions induced in the nanowires arrays and the thermal stresses (radial, azimuthal and axial stresses), which appear during the cooling of the system (nanowire and alumina template) from room temperature to 3 K was evaluated. The analysis of thermal induced stresses provides useful informations concerning the magnetic anisotropy in the Co nanowires. The temperature dependence of the remanent magnetization and coercitive field as an effect of the induced thermal …
Superconductivity Close To Magnetic Instability In Fe(Se1−Xtex)0.82, M H. Fang, H M. Pham, B Qian, T J. Liu, E K. Vehstedt, Y Liu, L Spinu, Z Q. Mao
Superconductivity Close To Magnetic Instability In Fe(Se1−Xtex)0.82, M H. Fang, H M. Pham, B Qian, T J. Liu, E K. Vehstedt, Y Liu, L Spinu, Z Q. Mao
Physics Faculty Publications
We report our study of the evolution of superconductivity and the phase diagram of the ternary Fe(Se1−xTex)0.82 (0≤x≤1.0) system. We discovered a superconducting phase with Tc,max=14 K in the 0.30.82, which exhibits an incommensurate antiferromagnetic order. We discuss the relationship between the superconductivity and magnetism of this material system in terms of recent results from neutron-scattering measurements. Our results and analyses suggest that superconductivity in this class of Fe-based compounds is associated with magnetic fluctuations and therefore may be unconventional in nature.
High-Frequency Characterization Of Permalloy Nanosized Strips Using Network Analyzer Ferromagnetic Resonance, Bijoy K. Kuanr, Radek Lopusnik, Leszek M. Malkinski, Matt Wenger, Minghui Yu, Donald Scherer Ii, Z Celinski, R E. Camley
High-Frequency Characterization Of Permalloy Nanosized Strips Using Network Analyzer Ferromagnetic Resonance, Bijoy K. Kuanr, Radek Lopusnik, Leszek M. Malkinski, Matt Wenger, Minghui Yu, Donald Scherer Ii, Z Celinski, R E. Camley
Physics Faculty Publications
We report on the dynamic properties of Permalloy nanostrips at gagahertz frequencies. The thickness of the strips is 100 nm, strip width is 300 nm, strip spacing is 1 μm, and length is 0.3–100 μm; aspect ratios are 1:1, 1:2, 1:3, 1:5, 1:10, and 1:333. The dynamic behavior was studied by network analyzer ferromagnetic resonance (FMR) using Permalloy strips on a coplanar waveguide in flip-chip geometry. The FMR mode frequencies (fr) can be controlled by the aspect ratio as well as by the applied magnetic field (H). In longer strips (1:10 and 1:333), …
Unusual Heavy-Mass Nearly Ferromagnetic State With A Surprisingly Large Wilson Ratio In The Double Layered Ruthenates (Sr1−Xcax)3ru2o7, Zhe Qu, Leonard Spinu, Huiqiu Yuan, Vladimir Dobrosavljevic, Wei Bao, Jeffrey W. Lynn, M. Nicklas, Jin Peng, Tijang Liu, David Fobes, Etienne Flesch, Z. Q. Mao
Unusual Heavy-Mass Nearly Ferromagnetic State With A Surprisingly Large Wilson Ratio In The Double Layered Ruthenates (Sr1−Xcax)3ru2o7, Zhe Qu, Leonard Spinu, Huiqiu Yuan, Vladimir Dobrosavljevic, Wei Bao, Jeffrey W. Lynn, M. Nicklas, Jin Peng, Tijang Liu, David Fobes, Etienne Flesch, Z. Q. Mao
Physics Faculty Publications
We report an unusual nearly ferromagnetic heavy-mass state with a surprisingly large Wilson ratio Rw (e.g., Rw∼700 for x=0.2) in double layered ruthenates (Sr1−xCax)3Ru2O7 with 0.08
Switching Behavior Of A Stoner–Wohlfarth Particle Subjected To Spin-Torque Effect, Dorin Cimpoesu, Alexandru Stancu, Leonard Spinu, Huy Pham
Switching Behavior Of A Stoner–Wohlfarth Particle Subjected To Spin-Torque Effect, Dorin Cimpoesu, Alexandru Stancu, Leonard Spinu, Huy Pham
Physics Faculty Publications
Recently, the current-induced spin-transfer torque has been proposed as a convenient writing process in high density magnetic random access memory. A spin-polarized current can switch the magnetization of a ferromagnetic layer more efficiently than a current induced magnetic field. Our paper discusses the switching properties of a Stoner–Wohlfarth magnetic particle for the case when spin torques and external field pulses are simultaneously present. The theoretical investigation of precessional motion is described by using Landau–Lifschitz–Gilbert equation with a spin-transfer torque term included. The main goal is to determine the parameters of field pulse for that the fast and stable switching can …
Size Dependence Of Static And Dynamic Magnetic Properties In Nanoscale Square Permalloy Antidot Arrays, Minghui Yu, Leszek Malkinski, Leonard Spinu, Weillie Zhou, Scott Whittenburg
Size Dependence Of Static And Dynamic Magnetic Properties In Nanoscale Square Permalloy Antidot Arrays, Minghui Yu, Leszek Malkinski, Leonard Spinu, Weillie Zhou, Scott Whittenburg
Physics Faculty Publications
Permalloy antidot arrays with different square hole sizes (1200×1200, 800×800, and 400×400 nm2) have been fabricated by means of electron-beam lithography and lift-off techniques. The smaller square hole size results in enhanced remanence and reduced coercivity in the antidot array. Multiple resonance modes were clearly observed for the magnetic field applied normal to the array plane, and double uniform resonance modes occurred when the field deviated more than 30° from the normal to the plane. Two distinct dipolar field patterns with different orientations and magnitudes split the uniform resonance into double resonance modes. The double resonance modes show …
Enhanced Spin-Dependent Tunneling Magnetoresistance In Magnetite Films Coated By Polystyrene, Wendong Wang, Leszek Malkinski, Jinke Tang
Enhanced Spin-Dependent Tunneling Magnetoresistance In Magnetite Films Coated By Polystyrene, Wendong Wang, Leszek Malkinski, Jinke Tang
Physics Faculty Publications
Hematite films were deposited by magnetron sputtering. A phase transformation from hematite to magnetite occurred when polystyrene (PS) coated hematite films were annealed above 200 °C in hydrogen flow. Giant negative magnetoresistance (MR) was observed with the best MR ratio of over 8% (at room temperature and in a field of 5.5 T) found in samples annealed at 230 °C. The temperature dependence of the resistivity is characteristic of intergranular tunneling. After the PS layer was removed and the films annealed again at 230 °C in hydrogen flow, the resistivity increased by about one order of magnitude and the MR …
Microwave Absorption Of Patterned Arrays Of Nanosized Magnetic Stripes With Different Aspect Ratios, Leszek M. Malkinski, Minghui Yu, Andriy Y. Voyk, Donald J. Scherer Ii, Leonard Spinu, Weillie Zhou, Scott Whittenburg, Zachary Davis, Jin-Seung Jung
Microwave Absorption Of Patterned Arrays Of Nanosized Magnetic Stripes With Different Aspect Ratios, Leszek M. Malkinski, Minghui Yu, Andriy Y. Voyk, Donald J. Scherer Ii, Leonard Spinu, Weillie Zhou, Scott Whittenburg, Zachary Davis, Jin-Seung Jung
Physics Faculty Publications
Arrays consisting of nanosized stripes of Permalloy with different length-to-width ratios have been fabricated using electron beam nanolithography, magnetron sputtering, and lift-off process. These stripes have a thickness of 100 nm, a width of 300 nm, and different lengths ranging from 300 nm to 100 μm. The stripes are separated by a distance of 1 μm. Magnetization hysteresis loops were measured using a superconducting quantum interference device susceptometer. Microwave absorption at 9.8 GHz was determined by means of ferromagnetic resonance technique. The dependence of the resonant field on the angle between the nanostructure and the in-plane dc magnetic …
Quantitative Method For Measurement Of The Goos-Hanchen Effect Based On Source Divergence Considerations, Jeffrey F. Gray, Ashok Puri
Quantitative Method For Measurement Of The Goos-Hanchen Effect Based On Source Divergence Considerations, Jeffrey F. Gray, Ashok Puri
Physics Faculty Publications
In this paper we report on a method for quantitative measurement and characterization of the Goos-Hanchen effect based upon the real world performance of optical sources. A numerical model of a nonideal plane wave is developed in terms of uniform divergence properties. This model is applied to the Goos-Hanchen shift equations to determine beam shift displacement characteristics, which provides quantitative estimates of finite shifts near critical angle. As a potential technique for carrying out a meaningful comparison with experiments, a classical method of edge detection is discussed. To this end a line spread Green’s function is defined which can be …
Dynamic And Temperature Effects In Toggle Magnetic Random Access Memory, Dorin Cimpoesu, Alexandru Stancu, Leonard Spinu
Dynamic And Temperature Effects In Toggle Magnetic Random Access Memory, Dorin Cimpoesu, Alexandru Stancu, Leonard Spinu
Physics Faculty Publications
In this paper we have studied the dynamic switching in magnetic random access memory (MRAM) and its dependence on thermal effects due to a finite temperature. The model is based on the Landau-Lifshitz-Gilbert equation and the stochastic Landau-Lifshitz-Gilbert equation which are numerically integrated. The magnetic layers are assumed to be ellipsoid shaped with each magnetic layer single domain. In addition, we have taken into account the uniaxial intrinsic anisotropy. Simulations were performed for both balanced and nonbalanced synthetic antiferromagnetic elements. The switching properties are discussed as a function of applied field pulses’ length and shape. In this paper we present …
Physics Of Complex Transverse Susceptibility Of Magnetic Particulate Systems, Dorin Cimpoesu, Alexandru Stancu, Leonard Spinu
Physics Of Complex Transverse Susceptibility Of Magnetic Particulate Systems, Dorin Cimpoesu, Alexandru Stancu, Leonard Spinu
Physics Faculty Publications
Complex transverse susceptibility is a recent proposed method for the determination of anisotropy and volume distributions in particulate magnetic media. So far, only thermal fluctuations and rate-dependent damped dynamics of the magnetic moment have been identified as reasons for the existence of the imaginary transverse susceptibility. In this paper, we apply a more general approach to derive the complex transverse susceptibility, and we show that the hysteresis phenomenon is the most general concept behind the existence of complex transverse susceptibility. In this paper, the physical origins of the imaginary part of transverse susceptibility are analyzed: rate-independent hysteresis, viscous-type rate-dependent hysteresis, …