High field magnetism of the high-T_c superconducting materials and related materials.

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The high-field magnetizations of R_2CuO_4 related compounds of high-T_c superconductors were investigated systematically in this year. The angular dependence of magnetization and the low temperature measurement of[110]direction are observed in Nd_2CuO_4. It is discovered that the two peaks of dM/dH at 1.3 K observed previously separate into three peaks below 1 K. This change may be related with the transition around 1 K given by the neutron diffraction study but detail is not known up to now. Next, the magnetization of Ce doped materials which show the superconductivity after the reduction treatment. The transition field and saturation field of Nd moment decrease as concentration of Ce increase but do not become zero at the concentration which is the onset of the superconductivity.The consideration of the multistep magnetization of Gd_2CuO_4 was done and it is inferred that the canting due to the Dzyaloshinski Moriya interaction of Cu-spins which is connected to Gd-spin by staggered field play important role on this anomalous magnetization. However, The frustration on the Gd spin system is important and further consideration is necessary.There is a problem that the ln T dependence on the electrical resistivity which is observed on Nd_<2-x>Ce_x, CuO_4 is the general character on all high-T_c superconductors. This effect is observed when the residual resistivity is enough large. Therefore, the test of the sample preparation with large residual resistivity is done with Dr. Hidaka(NTT). The experiment is possible to carry out and we applied the next year research project of Grant-in-Aid for Scientific Research.