層状化合物LaCoAsOおよび周辺物質の磁気的研究

概要

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We successfully synthesized itinerant-electron ferromagnetic compound LaCoAsO and studied its magnetic properties based on the self-consistent renormalization theory of spin fluctuations and Takahashis spin-fluctuation theory. We showed that the magnetization (M) of LaCoAsO shows the convex behavior when plotted in the form of M 2 vs H/M, while the M 4 shows the almost linear relation against H/M, which is predicted in the Takahashis theory. From the comparison between the experimentally observed magnetic susceptibility and calculated one by using the self-consistent renormalization theory, we showed that the nature of spin fluctuations is 3-dimensional around the Curie temperature TC, while above 3TC the difference between two susceptibilities becomes more prominent with increasing temperature, indicating that 2-dimensional spin fluctuations dominate over the 3-dimensional ones in the high temperature region.