大濱 哲夫

We performed zero-field nuclear magnetic resonance (ZF NMR) measurements of the antiferromagnetic and pressure-induced magnetically ordered phases of α-Mn at high pressures using a piston cylinder cell and an opposed-anvil high-pressure cell. We found that 55Mn internal magnetic fields disappeared discontinuously at 4.2–4.3 GPa. This suggests a first-order phase transition.

Abstract T’-La_1.8Eu_0.2CuO_4–y F _y (0 ≤ y ≥ 0.125) was measured by ^63,6BCu and ¹³⁹La NMR. This material is an electron-doped high-T_c cuprate superconductor which has Nd₂CuO₄-type structure (so-called T’-structure). The nuclear spin-lattice relaxation rate 1/T ₁ revealed that pseudogap behavior exists in the lightly electron-doped region of y ≤ 0.075 and electron doping suppresses the antiferromagnetic spin flutuations. These behaviors in electron-doped high-T _c cuprate superconductor are analogous with the optimum- and over-doped region in hole-doped type. ¹³⁹ La NMR spectra shows almost no antiferromagnetic region in the samples of T’-La_1.8Eu_0.2CuO_4–y F _y .

Abstract Comprehensive analyses of the ¹¹⁵In-NQR spectra employing a magnetic dipolar model and a transferred hyperfine model are performed to determine the magnetic structures of Ce₃PtIn₁₁. Based on this analysis, we confirmed that the magnetic moment at the Ce(1) site is very small (∼ 4% of that at the Ce(2) site) but finite. Further, for T_N2 < T < T_N1 and T < T_N2, the magnetic moments at the Ce(1) and Ce(2) sites are parallel to the c-axis, and the in-plane propagation vectors in the two Ce atoms sublattices are (q_a, q_b) = (1/2, 1/2). In the temperature interval T_N2 <T < T_N1, for example, both of them have a form of q = (1/2, 1/2, 0). For T < T_N2, the magnetic structure in the Ce(2) sublattice is defined by the propagation vector q = (1/2, 1/2, 1/2 or 0), whereas the Ce(1) sublattice forms a six-fold period structure given by q = (1/2, 1/2, 1/6).