Electron spin resonance of valence fluctuating compounds.

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1. High-magnetic field ESR High-field ESR spectrometer system using pulse magnet in the Research Center for Extreme Materials, Osaka, University was made to investigate the disappearance of band gap of valence fluctuating compounds. The test investigation is the study of Copper sulfate pentahydrate CuSO_45H_2O. The temperature dependent exchange interaction J_<AB> is found. [J.Phys.Soc.Jpn.57(1988)4366] Now we are using the ESR system to study not only valence fluctuating compounds but also heavy fermion materials.2.ESR study of GdB_6 The ESR study of GdBe single crystal was done to compare with the RB_6 type valence fluctuation compounds. The paramagnetic resonance of Gd^<3+> and the antiferromagnetic resonance was observed.3.ESR Study of Nd_2CuO_4 Electron spin resonance of neodymium copper oxide Nd_2CuO_4 is investigated and broad resonance is observed below 30K. The resonance is attributed to the Nd spin and no resonance from Cu spin is found. The g-value is isotropic with the value of 0.85 above 10K which is not so far from Nd<^<3+> free ion value of 0.73. Below about 5K, however, the g-value decreases rapidly with decreasing temperature with a large angular dependence. Effect of the Nd-Cu interactions on the Nd spin is suggest. [J. Phys. Soc. Jpn. to be published.]4.ESR study of valence fluctuating compounds. ( before 1987) 1)Electron spin resonance of Eu and Gd ions in SmB_6. [J.Magn.Magn.Mater. 52(1985)271-274.] 2)Higher harmonic electron spin resonance of Eu^<2+> in SmB_6. [J.Phys.Soc. Jpn. 55(1986)43-46.] 3)Electron spin resonance of disordered Sm ions in SmB_6. [J.Phys. Soc. Jpn. 55(1986)3737-3740.]