Takano Mikio

Field-Induced Ferromagnetism of Fe4+-Perovskite System, Sr1-xBaxFeO3 (0 ≤x≤1)

A series of cubic perovskite-type oxides, Sr1-xBaxFe4+O3 (\(0 \leq x \leq 1\)), have been studied through measurements of neutron diffraction and magnetization. It has been found that their helical spin structure changes from the G-type to the A-type with increasing Ba content at \(x \sim 0.85\). The application of an external magnetic field induces ferromagnetism with \({\sim}3.5\) µB/Fe, and the strength of the critical field decreases markedly from 39 T for SrFeO3 to 0.3 T for BaFeO3. The transition process can be categorized into three: SrFeO3, Sr0.4Ba0.6FeO3, and BaFeO3 types.

Cu NQR and NMR Studies of Optimally Doped Ca2-xNaxCuO2Cl2

Department of Physics, Graduate School of Science, Kyoto Sangyo University, Kyoto 603-8555, Japan Superconductivity Research Laboratory, International Superconductivity Technology Center, Koto, Tokyo 135-0062, Japan Osaka Prefecture University, Sakai 599-8531, Japan Materials and Structures Laboratory, Tokyo Institute of Technology, Yokohama 226-8503, Japan Institute for Chemical Research, Kyoto University, Uji, Kyoto 611-0011, JapanWe report on Cu nuclear quadrupole resonance (NQR) and NMR studies of an optimally hole-doped superconductor Ca2-xNaxCuO2Cl2 (Tc ~ 28 K for x ~ 0.2). In spite of robust oxygen composition, we observed a multiple broad NQR frequency spectrum and nonexponential Cu nuclear spin-lattice relaxation, being similar to those of La2-xSrxCuO4-d.