Giant Magnetoresistance Effect on Magnetic Ordered RNiSn-type Crystals with Long Period Spin Structure

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The series of RNiSn-type crystals has similar crystal structure, where R is a rare-earth atom. Their magnetic characteristics, however, are different each other. Especially, the rare-earth atom with large orbital moment shows metamagnetic characteristics, which has stepwise magnetization process. The change in magnetoresistance under the magnetic fields corresponds well to the region of the field induced magnetic phase.CeNiSn, at first, gathered the attention of many researchers as a typical Kondo semiconductor sample. The semiconductor nature, however, has been denied recently by the investigation for high quality and quite low impurity samples. The result presented one interesting and important problem of the metal-semiconductor (insulator) transition mechanism with the presence of extremely low impurity concentration. The problem inspired us to investigate the investigation of the resistivity of the magnetic ordered crystals. Especially, difference of the residual resistivity or non … More magnetic scattering for each magnetic phase in one crystal is one of the most interesting subject.The analysis method of the resistivity in the magnetic ordered crystal, however, has not been established well, so far. This subject belongs to the recent problem of highly correlated electron system and the exact solution of the resistivity problem in the magnetic material has not been expected. The resistance data, however, gives us the important information around the Fermi energy level and the analysis of it is quite important procedure.In this project, we could develop the new simple method to analyze the resistance data in the magnetically ordered crystals under the simple but clear assumptions. The method was applied to the magnetoresistance problem in TbNiSn, which shows various metamagnetic transition up to the field of 7T.The analysis concludes following quite interesting results : the coherence of the conduction electron spin system between both phase across the phase transition temperature at 2.1K is quite deference. The coherence strongly depends on the spin fluctuation or magnetic stability of the magnetic phase. The discovery of field induced phase and their spin fluctuation effect is also analyzed by use of the new method. It is considered that the new analysis method will plays important roll from now in the analysis and the physical interpretation based on the magnetoresistance data in the highly correlated electron systems. Less