The coercivity mechanism of Nd-Fe-B thin film samples with and without Nd deposition was investigated by simultaneous chemical and magnetic imaging by means of X-ray magnetic circular dichroism-photoemission electron microscopy. The two Nd-Fe-B thin film samples exhibited almost the same surface morphology and magnetic domain patterns, but their coercive fields were quite different, being 0.98 ...

This paper is the third and last part of a work attempting to give a unified analysis of Discontinuous Galerkin methods. The purpose of this paper is to extend the framework that has been developed in part II for two-field Friedrichs’ systems associated with second-order PDE’s. We now consider two-field Friedrichs’ systems with partial L2-coercivity and three-field Friedrichs’ systems with an e...

Single-phase Zr2Co11 nanomagnetic materials with high coercivity have been fabricated by melt spinning with subsequent annealing under Ar, N2, and vacuum. Annealing coarsens the grains and decreases the density of defects, leading to intergrain decoupling action and the enhancement of the magnetocrystalline anisotropy field of the hard magnetic phase. Therefore, coercivity increases 44.7% from ...

Co dot and antidot arrays with hexagonal symmetry have been prepared by combined electrochemical and sputtering techniques with significantly reduced nanoscale dimensions. Their magnetization reversal process has been analyzed on a macroscopic scale with Vibrating Sample Magnetometry (VSM) and on a microscopic scale by high spatial resolution Magnetic Transmission Soft X-ray Microscopy (MTXM). ...

We consider a finite element approximation of elliptic partial differential equations with random coefficients. Such equations arise, for example, in uncertainty quantification in subsurface flow modelling. Models for random coefficients frequently used in these applications, such as log-normal random fields with exponential covariance, have only very limited spatial regularity, and lead to var...

This work reports on the magnetic reversal of sub-μm sized elements consisting of an CoFeB/Ru/CoFeB artificial ferrimagnet (AFi). The elements were patterned into ellipses having a width of approximately 250 to 270nm and a varying aspect ratio between 1.3 and 8. The coercivity was found to decrease with an increasing imbalance of the magnetic moment of the two antiferromagnetically coupled laye...

The local magnetization profile along the length in magnetostrictive Fe-based magnetic microwires has been determined by magneto-optical Kerr effect. The study has been performed in microwires with different geometrical dimensions (i.e., diameter and length). The profiles of remanent magnetization and coercivity remain constant at the middle part for all microwires, whereas significant reductio...

Hiroyuki Yamamoto, Dr. Eng. Isao Kitagawa, Dr. Sc. Teruo Kohashi, Dr. Sc. Akira Sugawara, Dr. Eng. Takeshi Nishiuchi, Dr. Eng. OVERVIEW: Hitachi is working to improve the performance of the NdFe-B magnets that help make people’s way of life more energy efficient and reduce the load it places on the environment. To study the factors that govern coercivity, an important parameter of magnet perfor...

We study the classical first-kind boundary integral equation reformulations of time-harmonic acoustic scattering by planar soundsoft (Dirichlet) and sound-hard (Neumann) screens. We prove continuity and coercivity of the relevant boundary integral operators (the acoustic single-layer and hypersingular operators respectively) in appropriate fractional Sobolev spaces, with wavenumber-explicit bou...

The microstructure and magnetic properties, I,e. the initial susceptibility, coercivity and saturation magnetic polarization of nanocrystalline Fe73.5-~CoxCuiNb3Sii3.5Bi (x = 0 or 7) alloys with different volume fractions of crystalline and amorphous phases, are investigated. The crystalline phase in both conventionally annealed alloys (823 K for 1 h) has D03 ordered structure. However, after t...