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Aiming at nondestructive evaluation of magnetic materials, Monte Carlo simulations of the dynamic magnetic processes were investigated on the temporal and the temperature dependences for spin systems with various lattice imperfections as so called Barkhausen noises. From a physical point of view, the presented method might be the more useful tool for the analyses of the dynamic magnetic processes rather than those by Preisach model. We have been investigated on the Nondestructive Evaluations (NDE) of iron-based structural materials by detecting the magnetic property changes with increasing fatigues. Therefore, the observations of magnetic properties have been expected as a diagnosis method for NDE. For these purposes of NDE, many researchers have been studied on the magnetic properties of structural materials (1-9). Figure 1 shows an example of experimentally observed Barkhausen Noises (BN) spectra at a sample position as a function of applied field up to 14 mT with different yoke angles against the sample elongation direction for an iron-based material (A533B) with a residual stress caused by a tensile stress of 600 MPa. The alphabets in this figure indicated by "a"-"l" stand for the different yoke angle directions against the sample elongating direction. The spectrum of "g" was observed with a magnetic yoke pair (N-S) configuration in the perpendicular direction against the long sample. Here, the spectra of "a" and "l" stand for the observations in the parallel direction with the sample. As it is apparently seen, the BN spectra show large dependences on the observed yoke directions. Further, experimental results vary with the complicated combinations of the observing positions, angles, sample shape, preparations, annealing conditions, sample history, ambient temperatures and the chemical compositions. The microscopic processes and the method of the analyses for BN, therefore, have not been sufficiently studied due to this complexity. The difficulty of BN analysis seems to be cause by the dynamic process including localized magnetic potentials and by the transient de-pinning processes. By these reasons, the itinerant model could not be adopted for these analyses. The Preisach model is neither applicable because the total M-H curves are composed of many miner loops describing the steady states even though dM/dH at each point could be defined. In this paper, we developed a special Monte-Carlo (MC) method with

Fe-Si alloy system was investigated on the magneto-resistance (MR) effects in a temperature range between 77K-RT and in high fields up to 30 T. The samples were prepared by sputtering Fe(200 nm) on n-Si(1 0 0) surface and variously annealed up to beta-FeSi2 are obtained. The MR effects were found small less than several %, negative at RT and positive at T=77 K for Fe-rich samples. For a sample at the stoichiometric beta-Fe-Si-2 on n-Si as a p-n junction, we found a positive MR as large as 30% at RT in B = 30 T. The physical mechanism of the large MR is tentatively given by the carrier freeze-out effect in between the p-n. (c) 2006 Elsevier B.V. All rights reserved.

Giant negative magnetoresistance (MR) up to 15 % were observed for nano-scaled grains of Ni1-xMnx(0.23

Magnetic and magnetoresistance effect of needle shaped crystal and slightly Co rich Ca3Co2O6 was investigated in a temperature range between 2 and 100 K and in a dc magnetic field range less than 7 T and in pulsed fields less than 20 T. We found 1/3m(s) and 2/3m(s) plateaus of the magnetization for the full magnetization m, and large negative magnetoresistance effect of 10% at the same magnetic fields, respectively. (c) 2006 Elsevier B.V. All rights reserved.

A series of compounds, [Ni(AA)2X]Y (AA=diamines, tetramines etc; X=N 3 − and NO 2 − ; Y=ClO 4 − , PF 6 − etc) with S=1 have been synthesized, and their magnetic properties and crystal structures have been investigated. They have linear-chain structures. It has been found that the magnitude of the Haldane gaps can be controlled by substituting the bridging groups(X) and in-plane ligands(AA). On the other hand, [Ni([15]aneN 4 )N 3 ]PF 6 , [Ni([14]aneN 4 )N 3 ]ClO 4 ·H 2 O and [Ni(en) 2 NO 2 ]BF 4 show spin glass behaviors.