Showing papers on "Magnetic anisotropy published in 1997"
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01 Jan 1997
TL;DR: Magnetic properties of magnetism have been studied in a wide range of applications, including magnetism of amorphous materials, magnetism and magnetostriction as mentioned in this paper, spin distribution and domain walls.
Abstract: 1. Magnetostatic phenomena 2. Magnetic measurements 3. Atomic magnetic moments 4. Macroscopic experimental techniques 5. Magnetic disorder 6. Ferromagnetism 7. Antiferromagnetism and ferrimagnetism 8. Magnetism of metals and alloys 9. Magnetism of ferromagnetic oxides 10. Magnetism of compounds 11. Magnetism of amorphous materials 12. Magnetocrystalline anisotrophy 13. Induced magnetic anisotropy 14. Magnetostriction 15. Observation of domain structures 16. Spin distribution and domain walls 17. Magnetic domain structure 18. Technical magnetization 19. Spin phase transition 20. Dynamic magnetization 21. Various phenomena association with magnetization 22. Engineering applications of magnetic materials
1,486 citations
TL;DR: In this paper, a simple self-aligned process was used to fabricate magnetic tunnel junctions down to submicron sizes using optical and electron-beam lithography, and the shape of the field response of the magnetoresistance was varied by adjusting the shape anisotropy of one junction electrode.
Abstract: We have used a simple self-aligned process to fabricate magnetic tunnel junctions down to submicron sizes Optical and electron-beam lithographies were used to cover a range of areas spanning five orders of magnitude The bottom magnetic electrodes (Co or permalloy) in our junctions were exchange biased by an antiferromagnetic layer (MnFe) The top electrodes were made of soft magnetic materials (Co or permalloy) We have consistently obtained large magnetoresistance ratios (15%–22%) at room temperature and in fields of a few tens of Oe The shape of the field response of the magnetoresistance was varied from smooth to highly hysteretic by adjusting the shape anisotropy of one junction electrode
410 citations
TL;DR: In this article, the magnetic properties of arrays of submicronic (35 nm-500 nm) Ni and Co wires fabricated by electrodeposition into the cylindrical pores of track-etched polymer membranes are reported.
Abstract: We report on the magnetic properties of arrays of submicronic (35 nm-500 nm) Ni and Co wires fabricated by electrodeposition into the cylindrical pores of track-etched polymer membranes. This work reveals intrinsic differences between the magnetization reversal mechanisms taking place in these two systems. For Ni, the crystal anisotropy is small compared to the shape anisotropy and the magnetization lies along the wire axis. In contrast, the strong crystal anisotropy of Co and the orientation of the crystal easy axis (nearly perpendicular to the wire axis), allows for the appearance of a multidomain magnetization configuration, each domain being oriented partially along the normal to the wire axis. Experimental evidence for the existence of this multidomain configuration has been obtained from resistivity and magnetization measurements. Large scale micromagnetic calculations for Co and Ni wires with high aspect ratios corroborate the strong influence of the crystal anisotropy on the overall properties of Co wires and provide an accurate microscopic description of the nucleation fields and the magnetization reversal mechanism for Ni wires.
316 citations
TL;DR: In this article, the importance of the role of strain in La 0.7Sr0.3MnO3 thin films on SrTiO3 and LaGaO3 substrates was shown by revealing the dominance of stress anisotropy effects over magnetocrystalline anisotropic effects in the magnetic properties of these films.
Abstract: We show the importance of the role of strain in La0.7Sr0.3MnO3 films by revealing the dominance of stress anisotropy effects over magnetocrystalline anisotropy effects in the magnetic anisotropy of these films. Magnetic anisotropy measurements of (001) and (110) La0.7Sr0.3MnO3 thin films on SrTiO3 and LaGaO3 substrates, with excellent structural quality, reveal twofold symmetry on (110) La0.7Sr0.3MnO3 films and fourfold symmetry on (001) films. Such symmetries can only be explained by stress anisotropy contributions in the plane of the film. In conjunction with the thickness dependence of the magnetic properties, the results indicate the dominant role of strain in the magnetic properties of these doped manganites.
270 citations
TL;DR: The magnetic properties of Ca 3 Co 2 O 6 have been studied by magnetic susceptibility and neutron diffraction methods from 5 K to room temperature as discussed by the authors, and an effective magnetic moment of 5.7±0.2 μ B was found.
211 citations
TL;DR: In this article, the transport and magnetic properties of epitaxial (La07Sr03)MnO3 (LSMO) films deposited on LaAlO3 and SrTiO3 are compared.
201 citations
TL;DR: The magnetic properties of molecular beams of Fe, Co and Ni clusters deflected with a Stern-Gerlach magnet are reviewed in this article, where single-sided cluster deflections are observed indicating the occurrence of spin relaxation processes within isolated clusters.
200 citations
TL;DR: In this article, a diluted magnetic semiconductor, (Ga, Mn)As, with Mn composition x up to 0.07 was prepared by molecular-beam epitaxy on GaAs substrate at temperatures ranging from 160 to 320°C.
196 citations
TL;DR: In this article, the nucleation field for a small ferromagnetic prolate spheroid is calculated as a function of its size, its elongation, and the angle between the applied field and the sphroid axis.
Abstract: The nucleation field is calculated for a small ferromagnetic prolate spheroid as a function of its size, its elongation, and the angle between the applied field and the spheroid axis. If there is no other switching mode except for magnetization curling and coherent rotation, these results probably represent the coercivity. The calculation is rigorous only for an isotropic particle, but a first order approximation is also given for a uniaxial or cubic anisotropy whose easy axis is parallel to the long axis of the spheroid.
157 citations
TL;DR: In this paper, the magnetic switching of a continuous Permalloy film is artificially modified by lithographically structuring an antidot array, which introduces a spatially variant shape anisotropy field that competes with the intrinsic uniaxial anisotropic of the continuous film.
Abstract: The magnetic switching of a continuous Permalloy film is artificially modified by lithographically structuring an antidot array. The antidots introduce a spatially variant shape anisotropy field that competes with the intrinsic uniaxial anisotropy of the continuous film. This results in a well-defined periodic domain structure at remanence as observed by scanning Kerr microscopy, and which could be significant for high-density data storage. A micromagnetic calculation explains the structure and indicates optimum anisotropy conditions for data storage applications.
153 citations
TL;DR: In this paper, the magnetic properties of Ca 3 Co 2 O 6 with ferromagnetic Ising chains have been studied using oriented sample along the chain direction, and it is suggested that an octahedral Co 3+ is nonmagnetic, whereas a trigonal prismatic Co 3+, has a fictitious spin S '=1 with large single-ion anisotropy (D ∼-25 K, g // ∼4).
Abstract: Magnetic properties of Ca 3 Co 2 O 6 with ferromagnetic Ising chains have been studied using oriented sample along the chain direction. From the extremely anisotropic behavior in its magnetization at low temperatures and in the temperature dependence of magnetic susceptibility, it is suggested that an octahedral Co 3+ is nonmagnetic, whereas a trigonal prismatic Co 3+ has a fictitious spin S '=1 with large single-ion anisotropy ( D ∼-25 K, g // ∼4). At low temperatures below 5 K, multisteps are observed in the magnetization, suggesting the existence of various magnetic structures. The pulsed magnetization measurements reveal that the response of ferromagnetic chains to the field is slow and varies as a function of temperature and Δ H /Δ t .
TL;DR: In this article, a strontium ferrite/polyimide composite thin film was fabricated and characterized for micromachining applications and a simple magnetic microactuator made with those materials has been fabricated and tested.
Abstract: In this work, strontium ferrite/polyimide composite thin films are fabricated and characterized for micromachining applications. The application of these materials in microelectronics and micromachining dictates the use of different polymers than those previously used for conventional plastic magnets due to fabrication compatibility constraints. The material investigated here consists of magnetically anisotropic strontium ferrite particles suspended in a benzophenone tetracarboxylic dianhydride-oxydianiline/metaphenylene diamine polyimide matrix. Magnetic mechanical, and processability properties of these composites are investigated for a strontium ferrite loading range of 55%-80% by volume. Intrinsic coercivity H/sub ci/ residual magnetic flux density B/sub r/ and maximum energy product (BH)/sub max/ have been determined. For an 80% by-volume concentration loading of ferrite, H/sub ci/ of 318 kA/m B/sub r/, approaching 0.3 T, and (BH)/sub max/ of 11900 T/spl middot/A/m have been achieved. Biaxial Young's modulus and residual stress are determined using a slightly modified in situ load/deflection technique. The biaxial Young's modulus increases with increasing the magnetic powder loading. The materials have been deposited and patterned using two techniques: (1) screen-printing and (2) spin-casting, followed by photolithography. Finally, a simple magnetic microactuator made with those materials has been fabricated and tested, which demonstrates the usefulness of those materials to micromachining.
TL;DR: In this paper, shape anisotropy was used to control the response characteristics of magnetic tunnel junctions, and the resistance versus field curve was made to vary from a nonhysteretic linear curve with a high-field sensitivity (0.3%/Oe) to a hystertic response curve with high squareness.
Abstract: We show that shape anisotropy can be used to control the response characteristics of magnetic tunnel junctions. By varying the junction shape, the resistance versus field curve was made to vary from a nonhysteretic linear curve with a high-field sensitivity (0.3%/Oe) to a hysteretic response curve with high squareness.
TL;DR: In this paper, a detailed study of the magnetization reversal dynamics in ultrathin cobalt films (t Co = 6-12 A ) sandwiched by gold (1 1 1) layers, their magnetic anisotropy being perpendicular to the film surface, is presented.
TL;DR: In this article, it was shown that when the constraint of this symmetry is removed, other modes are also possible, but their lowest resonance frequency is very nearly the same as that of one of the cylindrically symmetric modes.
Abstract: Exchange resonance modes in small ferromagnetic spheres were first predicted for the case of a cylindrical symmetry of the magnetization configurations. It is shown here that when the constraint of this symmetry is removed, other modes are also possible, but their lowest resonance frequency is very nearly the same as that of one of the cylindrically symmetric modes. Therefore, new resonances may only be sought at higher frequencies than those observed in the most recent experiment. It is also shown that the dependence on the particle size observed in that experiment may be accounted for by assuming a rather strong surface anisotropy in the measured spheres. The original prediction of an R−2 dependence, typical for the curling mode, may still be reached if either the particle size or the surface anisotropy is considerably reduced.
TL;DR: In this paper, the authors used a magnetron sputtering onto Cr(211) and (100) buffer layers, respectively, to grow Epitaxial Sm-Co(1100 and (1120) films, which exhibit uniaxial in-plane anisotropies of ≈20-25 T and room-temperature coercive fields that increase to 4.1
Abstract: Epitaxial Sm–Co(1100) and (1120) films have been grown by magnetron sputtering onto Cr(211) and (100) buffer layers, respectively. The Sm–Co(1100) films exhibit uniaxial in-plane anisotropies of ≈20–25 T and room-temperature coercive fields that increase to 4.1 T as the film thickness decreases to 75 A. The 3 T coercivities of the (1120) films are independent of thickness.
TL;DR: In this paper, the intrinsic anisotropy of the dangling bonds at the GaAs(0 0 1) surface was investigated and shown to be a useful property for future memory or switching applications.
TL;DR: In this paper, a detailed study by magneto-optical techniques of in-plane magnetization reversal behaviour in epitaxial Fe films grown by MBE on (10 0) oriented MgO substrate was undertaken.
TL;DR: In this article, a circular x-ray dichroism technique is presented that allows the determination of the microscopic origin of the spin reorientation transition in ultrathin single-crystalline cobalt/nickel films.
Abstract: Understanding of the magnetocrystalline anisotropy in magnetic materials (the influence of different elemental components on the direction of easy magnetization) can be greatly enhanced by measuring the orbital moment anisotropy of the elemental constituents. A circular x-ray dichroism technique is presented that allows the determination of the microscopic origin of the spin reorientation transition in ultrathin single-crystalline cobalt/nickel films. The stronger anisotropy contribution of a much thinner cobalt layer redirects the easy magnetization direction of the entire film.
TL;DR: In this paper, the authors demonstrate that highly ordered equiatomic FePd thin layers can be grown in the L1 0 structure using Molecular Beam Epitaxy, which exhibits a strong perpendicular magnetic anisotropy.
TL;DR: The accuracy of an inclination shallowing correction technique was tested on the remanence of the Paleocene Nacimiento Formation in this article, and the inclination-corrected formation mean direction was indistinguishable from the direction predicted by North America's Paleocene paleopole.
Abstract: The accuracy of an inclination shallowing correction technique was tested on the remanence of the Paleocene Nacimiento Formation. The correction assumes that changes in paleomagnetic inclination during deformation will be directly related to changes in remanence anisotropy. The remanence anisotropy is also a function of the magnetic anisotropy of the individual magnetic grains. The Nacimiento Formation was selected for this test because its inclination is shallow by 7° to 8° and previous paleomagnetic studies indicate that it has a primary remanence with a well-constrained age and that magnetic overprints are minimal. Tectonics are an unlikely explanation for its shallow inclination. These conditions allow the inclination-corrected remanence to be compared to a well-defined paleomagnetic pole to determine the accuracy of the technique. The characteristic remanence from 20 Nacimiento sites was isolated by alternating field and thermal demagnetization and was corrected using the anisotropy of anhysteretic remanence measured for three to five samples per site. Individual particle anisotropy was determined by drying a magnetic separate/epoxy mixture in a 35–50 mT magnetic field. Laboratory compaction of disaggregated Nacimiento material was also used to yield an effective individual magnetic particle anisotropy. The two techniques resulted in similar values for individual particle anisotropy and similar inclination shallowing corrections. Both corrections were successful, and the inclination-corrected formation mean direction was indistinguishable from the direction predicted by North America's Paleocene paleopole. The inclination shallowing correction technique reported here should be applied routinely in paleomagnetic studies, provided that the remanence is a primary depositional remanence that has been affected only by syndepositional or early postdepositional processes (e.g., compaction).
TL;DR: In this article, a magnetic fourfold anisotropy was found for the permalloy micron dot lattice with diameters of 1 μm and a dot separation of 0.1 μm.
Abstract: Static magnetic and spin wave properties of square lattices of permalloy micron dots with thicknesses of 500 and 1000 A and with varying dot separations have been investigated. A magnetic fourfold anisotropy was found for the lattice with dot diameters of 1 μm and a dot separation of 0.1 μm. The anisotropy is attributed to an anisotropic dipole–dipole interaction between magnetically unsaturated parts of the dots. The anisotropy strength (order of 105 erg/cm3) decreases with increasing in-plane applied magnetic field.
TL;DR: The magnetic structure of wedge-shaped Co/Au(111) films has been analyzed in the thickness range of around five monolayers where a reorientation transition takes place as discussed by the authors.
Abstract: The magnetic structure of wedge-shaped Co/Au(111) films has been analyzed in the thickness range of around five monolayers where a reorientation transition takes place The detection of two critical thicknesses with an apparently new phase in between them can be understood by evoking general considerations of stability and coexistence of phases The analysis in terms of thickness-driven evolution in the anisotropy space of the system leads to the determination of the surface anisotropy constants of first and second order in a most direct and consistent manner {copyright} {ital 1997} {ital The American Physical Society}
TL;DR: In this paper, the magnetization reversal and magnetoresistance behavior in lithographically defined structures based on a 400 A Ni80Fe20 film was studied and the magnetic anisotropy was observed as a function of orientation of applied field in submicron structures.
Abstract: We have studied the magnetization reversal and magnetoresistance behavior in lithographically defined structures based on a 400 A Ni80Fe20 film The structures consist of square arrays of holes with size d in the range from 05 to 15 μm fabricated using electron beam lithography and an optimized pattern transfer process For the field applied along the intrinsic easy axis, a marked increase in the coercive field is observed as the hole size is decreased This has been attributed to the pinning of the domain walls in the vicinity of the holes However, for the field applied along the intrinsic hard axis direction, there is a marked increase in the remanence as the hole size is reduced due to the competition between the intrinsic uniaxial anisotropy field and the shape induced magnetic anisotropy field Unusual magnetoresistance effects are observed as a function of orientation of applied field in submicron structures
TL;DR: In this article, the magnetization reversal process in arrays of sub-micron Ni and Co wires was investigated by means of magnetization and torque experiments together with micromagnetic calculations.
Abstract: We have investigated the magnetization reversal processes in arrays of sub-micron Ni and Co wires by means of magnetization and torque experiments together with micromagnetic calculations. The wires were produced by electrodeposition in the cylindrical pores of track-etched polymer membranes. Diameters in the range 35–400 nm have been studied. The arrays of Co and Ni nanowires display different magnetic behaviors. Particular emphasis is given to the competing shape and crystal magnetic anisotropies that exist in the Co nanowire system. In both systems, explaining the experimental results requires domain formation, except for the smallest diameters where single domain behavior occurs.
TL;DR: In this article, the authors model a sill as a steadystate flow of a Bingham fluid, driven by a pressure gradient in a horizontal conduit, and calculate the magnetic susceptibility for a large number of grains with a uniform distribution of initial orientations.
Abstract: SUMMARY Volcanic rocks forming sills, dykes or lava flows may display a magnetic anisotropy derived from the viscous flow during their emplacement. We model a sill as a steadystate flow of a Bingham fluid, driven by a pressure gradient in a horizontal conduit. The magma velocity as a function of depth is calculated from the motion and constitutive equations. Vorticity and strain rate are determined for a reference system moving with the fluid. The angular velocity and the orientation of an ellipsoidal magnetic grain immersed in the fluid are calculated as functions of time or strain. Magnetic susceptibility is then calculated for a large number of grains with a uniform distribution of initial orientations. It is shown that the magnetic lineation oscillates in the vertical plane through the magma flow direction, and that the magnetic foliation plane changes periodically from horizontal to vertical. The results are compared with the magnetic fabric of Ferrar dolerite sills (Victoria Land, East Antarctica) derived from low-field susceptibility measurements.
TL;DR: In this article, a large magnetoresistance (83%) at low magnetic fields of tens of Oe at 4.2 K in the epitaxial trilayer junction structure, La0.67Sr0.33MnO3/SrTiO3, was reported.
Abstract: We report the observation of a large magnetoresistance (83%) at low magnetic fields of tens of Oe at 4.2 K in the epitaxial trilayer junction structure, La0.67Sr0.33MnO3/SrTiO3/La0.67Sr0.33MnO3. The spin-polarization parameter of the manganite has been determined from the magnetoresistance value. The switching fields of the two magnetic layers were designed by using the magnetic shape anisotropy. By limiting the sweeping field in a low field range (∼100 Oe), we have achieved bistable resistive states at zero field, which is of potential interest for magnetoelectronic applications.
TL;DR: In this paper, the distribution of energy barriers (E b ) of an assembly of small magnetic particles with a median diameter of 70 A was analyzed. But the system is not adequately described by the commonly adopted log-normal distribution function, which comparably should yield an excess amount of large particles sizes.
TL;DR: In this paper, the magnetic viscosity and activation volume of elongated /spl alpha/Fe particles in alumite were investigated at room temperature for an anodized aluminum oxide film.
Abstract: Particle size effects on the magnetic viscosity and activation volume were studied at room temperature for elongated /spl alpha/-Fe particles in alumite (Fe nanowires in an anodized aluminum oxide film). Both magnetic viscosity and activation volume are strongly dependent on the particle diameter, but independent of the particle length. The magnetization reversal mechanism of elongated /spl alpha/-Fe particles in alumite films is discussed. The activation volume may represent the size of the magnetic switching unit propagating along the particle length during the non-uniform magnetization reversal.
TL;DR: In this article, a selfconsistent relativistic spin-polarized version of the total-energy FLAPW method is developed on the basis of a second-variation treatment of the spin-orbit coupling (SOC).
Abstract: A self-consistent relativistic spin-polarized version of the total-energy full-potential linearized-augmented-plane-wave (FLAPW) method is developed on the basis of a second-variation treatment of the spin-orbit coupling (SOC). As illustration, the method is applied to determine the magnetoelastic coupling, orbital magnetic moment anisotropy and magnetic anisotropy energy (MAE) of a Co overlayer on Cu(001). The MAE (-0.36 meV) calculated at the equilibrium overlayer/substrate distance is in good agreement with experiment. As discovered earlier by Wu and Freeman, we find a linear dependence of the MAE on the overlayer/substrate distance. The calculated positive effective magnetoelastic coupling coefficient (1.13 meV) is caused by a positive surface magnetoelastic anisotropy (0.23 meV). This causes a negative magnetostriction coefficient ${\ensuremath{\lambda}}_{001}=\ensuremath{-}5.20\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}5}$ and an isotropic magnetostriction coefficient ${\ensuremath{\lambda}}_{s}=\ensuremath{-}5.65\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}5}$ that is in very good agreement with previous studies based on a perturbative SOC treatment.