Papers by Keyword: Magnetocrystalline Anisotropy

Abstract: Among magnetic materials, ferrites have significant attention due to their potential application, such as magnetic recording, sensors, radar-absorbent materials, catalysts, and energy-storage devices. One of the ferrites family, FeMnO₃, has been synthesized by solid-state reaction using Fe₂O₃ powder with an excess of 0.02% MnO₂ powder in the stoichiometric composition. The structural and morphological properties have been performed using XRD and SEM at room temperature. The diffraction peaks in the pattern were indexed as FeMnO₃ with a cubic (bixbite, Ia3) crystal structure. It showed no additional peaks due to impurities. The SEM image reveals the grains nucleate in a cube-like shape. Some of the particles also seem to agglomerate into larger particles. The magnetic characterization was carried out using VSM at room temperature. The magnetic hysteresis loop (M-H curves) notices the ferrimagnetic behavior. The results show remnant magnetization (M_r), coercive field (H_c), magnetic moment (µ_B), and anisotropy constant of FeMnO₃ are 0.296 emu/g, 299 Oe, 0.046 emu/mol, and 0.1 when the external field is 70˚-80˚ from the easy axis, respectively.

Abstract: (Fe,Ni)₂(P,Si) compounds were synthesized and characterized. Ni substitution in Fe_1.95-xNi_xP_0.7Si_0.3 is found to favor the formation of Fe₂P-type hexagonal structure. The samples appear nearly single phase. Powder oriented in the magnetic field shows a pronounced uniaxial magnetic anisotropy with c axis as the easy axis. Magnetization measurements carried out along and perpendicular to the c crystal axis demonstrate a significant magnetic anisotropy, making these materials potential candidates for permanent magnet applications. We found that (Fe,Ni)₂(P,Si) compound has no remanent magnetic field and coercivity, but it has a large magnetocrystalline anisotropy at room temperature. Therefore, doping Fe₂P type compounds with a small amount of Ni and Si may be a promising way to create new materials with large magnetocrystalline anisotropy at room temperature, and thus rare-earth free permanent magnet.

Abstract: The phase composition, structural parameters, and basic magnetic characteristics of BaFe₁₂O₁₉ hexaferrites prepared by the mechanochemical synthesis with subsequent annealing at a temperature of 1000°С and 1100°С for 1 h are investigated. The influence of the annealing temperature on the properties of synthesized materials is analyzed. Values of the saturation magnetization and the anisotropy field are determined. It is established that annealing temperature in the interval 1000 - 1100 °C does not significantly affect on the phase composition and the size of nanoparticles. The value of the anisotropy field increases substantially with increasing temperature.

Abstract: We report on an experimental study on electrodeposited nanocrystalline nickel films. Scanning electron and atomic force microscopies reveal granular structure of the films with varying grain size and surface roughness in dependence on deposition conditions. In term of magnetic properties all the fabricated films are isotropic. We define magnetization reversal occurring through the non-coherent magnetization rotation where the average grain size is comparable to the width of Bloch domain walls (DW). For those film with a greater grain size, the remagnetization processes take place due to the non-coherent magnetization vectors rotation and DW displacement in the grains.

Abstract: In this study, we have substituted Mg into cobalt ferrite to investigate the effect on magnetic properties. The effect is different compared to other cation substitution studies on cobalt ferrite. An interesting observation is that the variation of magnetocrystalline anisotropy, due to Mg-substitution, is comparable with increasing Mg concentration. Similar trend was previously reported on the effect of Mg-substitution of the magnetostrictive properties of cobalt ferrite. Coercive field varies more significantly with Mg-substitution.

Abstract: The composition dependence of crystal structure, lattice parameter, micromorphology, Curie temperatures, magnetocrystalline anisotropy constant of Tb_0.29Dy_0.48Ho_0.23(Fe_1-XMn_X)_1.95 (x0.3) alloys were investigated by the experiment. X-ray diffraction patterns demonstrate the Tb_0.29Dy_0.48Ho_0.23(Fe_1-XMn_X)_1.95 (x0.3) alloys possess MgCu₂-type cubic Laves structure. The lattice parameter of Tb_0.29Dy_0.48Ho_0.23(Fe_1-XMn_x)_1.95 alloy increases with increasing of x value. The Curie temperature T_c decreases from 375°C for x=0 to 316 °C for x=0.05, 265°C for x=0.1. The magnetocrystalline anisotropy constant K₁ of Tb_0.29Dy_0.48Ho_0.23(Fe1_-xMn_x)_1.95 (x0.3) decreases slightly with the increasing of x value. The magnetostriction was examined under applied magnetic field H in the room temperature. The Tb_0.29Dy_0.48Ho_0.23(Fe_1-xMn_x)_1.95 (x0.2) alloys have the character of giant magnetostrictive in room temperature. With the increasing of Mn concentration, the magnetostrictive of Tb_0.29Dy_0.48Ho_0.23(Fe_1-xMn_x)_1.95 (x0.2) alloy decreased.

Abstract: The crystal structure, Curie temperatures, spin reorientation temperature, magnetocrystalline anisotropy constant and magnetostriction of TbDyHoFe1.95 alloys with composition formulation (1-y)Tb0.36Dy0.64Fe1.95+yTb0.20Dy0.22Ho0.58Fe1.95 (0≤y≤1) were investigated. X-ray diffraction patterns demonstrate the TbDyHoFe1.95 alloys possess MgCu2-type cubic Laves structure. The Curie temperature Tc decreases slightly from 381 °C for Tb0.36Dy0.64Fe2 to 379 °C for y=0.3, 375°C for y=0.4 and 373°C for y=0.5. The spin reorientation temperature Tr increases from -94 oC for Tb0.36Dy0.64Fe2 to -70°C for y=0.3 and -51oC for y=0.5. The magnetocrystalline anisotropy constant K1 decreases with increasing y value. The magnetostriction was examined under applied magnetic field H (0

Abstract: Spin-reorientation transitions in intermetallic (Pr1-xSmx)Fe8Ga3C compounds with the tetragonal BaCd11-type structure have been investigated. The magnetic phase diagram has been proposed for these compounds based on magnetic and X-Ray diffraction studies using their nanocrystalline ribbons and powders aligned in a magnetic field. In the concentration range 0 ≤ x ≤ 0.4 the compounds exhibit an «easy-plane» anisotropy at all temperatures of the magnetically ordered state. The magnetic anisotropy of the compounds with 0.5 ≤ x ≤ 1 is of the «easy-cone» type. The SmFe8Ga3C compound with the highest Sm content is a uniaxial ferromagnet with no indications of a spin-reorientation transition below its Curie temperature.

Abstract: Structure as well as magnetic and magnetoelastic properties of nanocrystalline (Fe,Co)-(Hf,Zr)-Cu-B alloys (HITPERM-type) were investigated in order to find out which factors are responsible for the magnetic hardening of these magnetically soft materials. Magnetoelastic anisotropy, caused by the presence of cobalt, was found to play the predominant role in the observed increase of coercive field. On this basis, guidelines on chemical composition and crystallisation process selection were suggested for two fields of application: soft magnetic cores and sensors or actuators cores.

Abstract: We report the study of the magnetoresistance (MR) and resistivity as a function of temperature in epitaxial thin films of the La0.67Ca0.33MnO3 type (LCMO). The films deposited onto Y-cut of single-crystalline LiNbO3 (LNO) substrates by pulsed-laser deposition in an on-axis geometry. For comparison, the same manganite film deposited onto LaAlO3 (LAO) substrate is studied. The MR of LCMO/LNO film is found to be anisotropic and exhibits a hysteresis loops in low magnetic fields. When magnetic field is parallel to the film plane a number of jumps are observed in the MR below magnetic fields H~6 kOe. These jumps reflect the presence of pinning centers for domain walls. Evidently, a lattice deformation produced by a mismatch of lattice constants LCMO film and LNO, which lead to distortion of the film, is the origin of such strong pinning centers.