The magnetic properties of amorphous Fe were investigated by examining the electronic structures of structurally disordered Fe systems generated from crystalline bcc and fcc Fe using a Monte-Carlo simulation. As a rst principles band method, the real space spin-polarized tight-binding linearized-mun-tin-orbital recursion method was used in the local spin density approximation. Compared to the crystalline system, the electronic structures of the disordered systems were characterized by a broadened band width, smoothened local density of states, and reduced local magnetic moment. The magnetic structures depend on the short range configurations. The antiferromagnetic structure is the most stable for a bcc-based disordered system, whereas the noncollinear spin spiral structure is more stable for a fcc-based system.

Spin-orbit coupling (SOC) is a source of strong spin dephasing in two- and three-dimensional semiconducting systems. We report that spin dephasing in a two-dimensional electron gas can be suppressed by introducing a quantum point contact. Surprisingly, this suppression was not limited to the vicinity of the contact but extended to the entire two-dimensional electron gas. This facilitates the electrical control of the spin degree of freedom in a two-dimensional electron gas through spin-orbit coupling.

Combined study of in-situ stress measurements and atomic force microscopy (AFM) revealed drastic stress relaxation in the CoCrPt and PS(styrene)-PVP(vinyl pyridine) polymer hybrid structure that was closely related to the growth structure of the film. We have observed not only no large initial growth stress at the initial stages of film growth but also twice smaller stress in magnitude with opposite sign in the CoCrPt/PS-PVP/Si sample. The microstructural studies using AFM at the various film growth stages revealed that the film growth structure plays an important role in the stress relaxation mechanism of CoCrPt films on a corrugated polymer surface.

The relationship between ferromagnet anisotropic magnetization and the antiferromagnet atomic spin configuration was investigated for various angles of the uniaxial deposition magnetic field of the FeMn layer in the Corning glass/Ta(5nm)/NiFe(7nm)/FeMn(25nm)/Ta(5nm) multilayer that was prepared by the ion beam sputter deposition. The exchange bias field (H_ex) obtained from the measurement of the easy-axis MR loop decreased to 40 Oe at the deposition field angle of 45^o, and to 0 Oe at the angle of 90^o. When the difference between the uniaxial axis between the ferromagnet NiFe and the antiferromagnet FeMn was 90^o, the strong antiferromagnetic dipole moment of FeMn caused the weak ferromagnetic dipole moment of NiFe to rotate in the interface.

A new synthetic method for the formation of uniform α-Fe₂O₃ nanoparticles was reported and their magnetic properties were investigated. The sonochemical synthesis and the subsequent take-off technique resulted in spherical shaped α-Fe₂O₃ nanoparticles with an average diameter of 60 nm. The temperature- and applied magnetic field-dependent magnetization of the α-Fe₂O₃ nanoparticles was explained by the sum of two contributions, i.e., the Morin transition and superparamagnetism, because the critical size for superparamagnetism was within the size variation of the nanoparticles.

This study examined the crystallographic and magnetic properties of vanadium-substituted lithium cobalt titanium ferrite, Li_0.7Co_0.2Ti_0.2V_0.2Fe_1.7O₄. Ferrite was synthesized using a conventional ceramic method. The samples annealed below 1040 ^oC showed X-ray diffraction peaks for spinel and other phases. However, the sample annealed above 1040 ^oC showed a single spinel phase. The lattice constant of the sample was 8.351 Å, which was relatively unaffected by vanadium-substitution. The average grain size after vanadium- substitution was 13.90 ㎛, as determined by scanning electron microscopy. The Mössbauer spectrum could be fitted to two Zeeman sextets, which is the typical spinel ferrite spectra of Fe³⁺ with A and B sites, and one doublet. From the absorption area ratio of the Mössbauer spectrum, the cation distribution was found to be (Co_0.2V_0.2Fe_0.6)[Li_0.7Ti_0.2Fe_1.1]O₄. Vibrating sample magnetometry revealed a saturation magnetization and coercivity of 36.9 emu/g and 88.6 Oe, respectively, which were decreased by vanadium-substitution.

We studied the magnetic properties of TmFe₂O₄. The magnetization measurements revealed the magnetic ordering of Fe spins at around 240 K. The difference between zero-field-cooled (ZFC) and field-cooled (FC) magnetization was close to the thermoremanent magnetization (TRM), indicating the glass behavior exhibited by this material.

The effects of Cu-addition and die-upset temperature on the texture in the die-upset Nd-lean Nd_xFe_93.5-(x+y)- Cu_yGa_0.5B₆ (x = 9-12, y = 0-2) alloys were investigated. The die-upset Cu-containing Nd-lean Nd₁₂Fe_81.5-y- Cu_yGa_0.5B₆ (y = 1, 2) alloys showed a considerable texture. Texture in the Nd-lean alloys developed through basal plane slip deformation. The Cu-addition reduced the melting point of grain boundary phase facilitating grain gliding during the die-upsetting, and providing a greater chance for the Nd₂Fe₁₄B grains to meet the deformation conditions. Die-upsetting at higher temperature facilitated grain gliding and plastic deformation, thus enhancing texture.

The multi-degrees of freedom surface permanent-magnet motor (Multi-D.O.F. SPM) has several degrees of freedom operations that are defined as the “roll”, “yaw”, and “pitch”. Normally, the torque that is generated to rotate a rotor includes ripples. The analysis of the torque ripples is important for improving motor performance. In terms of the electric analysis, torque ripple occurs as a result of many factors, including the rotor and stator structures, the distribution of the air-gap flux density, and the waveform of the current in the coils. In particular, the torque ripple is an important factor in the stable operation of the Multi-D.O.F. SPM. Therefore, in this work, the torque ripple was analyzed using various types of magnetization for the permanent magnet. An improved model was proposed for the Multi-D.O.F. SPM based on this analysis.

This paper introduces two types of magnetization, and reports the effect of the magnetization direction on the iron loss in a brushless DC (BLDC) motor using a 2-D time-stepped voltage source finite-element method (FEM). The iron losses were found to consist of hysteresis and eddy current loss, which were calculated from the time variation of the magnetic field distribution. To confirm the analysis, a prototype BLDC motor was constructed with a sintered ferrite magnet. The analysis and experimental results suggest that the magnetization direction has a significant effect in terms of the iron loss characteristics of the BLDC motor.