[en] Taking account of the Meissner effect (B = 0 for the superconducting state), the vector potential A is defined not by B = rot A but by H = rot A to calculate the linear magnetic field response of a bulk superconductor. The magnetic interaction in the Bohm-Pines theory is consistently introduced into the Hamiltonian of the system. On the basis of both the usual linear response theory and the BCS-Bogolyubov theory, the static magnetic susceptibility χ = -1/4π, i.e. perfect diamagnetism, is obtained for the bulk superconductor at zero temperature. (orig.)

[en] The bulk magnetization of metallic Gd decreases with increasing pressure and disappears at 7 GPa. The Curie temperature reduces with pressure, and the ferromagnetic signals disappear above 7 GPa in the wider temperature region. These experimental results are discussed on the pressure induced frustration of the RKKY interactions among the ⁸S_7/2 state of localized 4f electrons

[en] Mixed antiferromagnets Ni_1−xM_xCl₂·2H₂O (M=Co, Mn) were prepared. The crystal structure of NiCl₂-2H₂O is a little different from that of CoCl₂·2H₂O and MnCl₂·2H₂O. In order to examine how Co or Mn spins in NiCl₂·2H₂O crystal structure behave, we determined precisely the phase transition temperatures by measuring the specific heats and have obtained the concentration dependence of the phase transition temperature. Substitution of Co for Ni increases a little the transition temperature and contrary to this the substitution of Mn decreases the transition temperature rapidly. The results are discussed on the basis of molecular field theory. In the case of M=Co, the concentration dependence of the phase transition temperature is well explained by molecular field theory. But, in the case of M=Mn, the molecular field theory cannot explain it sufficiently. Thus Mn spins in NiCl₂·2H₂O crystal show the peculiar behavior. We suppose that this may be attributed to a kind of the instability of Mn spins.

[en] Proton NMR of the diluted one-dimensional Heisenberg antiferromagnets has been observed by the conventional spin echo method in zero magnetic field below the Neel temperature. The temperature dependences of the spin-lattice relaxation rates 1/T₁ have been obtained. 1/T₁ in a pure system increases rapidly with the increasing temperature, which is attributed to the change of the relaxation mechanism from the two magnon to three magnon processes. A slight dilution caused the spin-lattice relaxation rates increase markedly at low temperatures. But at high temperatures, the temperature dependences of the diluted systems approach that of pure system. The results are discussed on the basis of the spin wave theory. The spin echo intensity decays as a function of the square of the interval time between two pulses. The temperature dependences of the spin-spin relaxation time T_2G measured from a Gaussian decay are reported, too.

[en] ⁶⁹Ga and ⁷¹Ga NMR signals in GdGa_2-xAl_x (x = 0.1, 0.25, 0.5, 0.75,1) have been observed at a low temperature in a zero magnetic field. Gd NMR signals were observed only for the samples with x ≤ 0.5 in the frequency range less than 110MHz, but Ga NMR signals have been observed for all samples in the frequency range higher than Gd NMR frequencies. The features of the observed Ga NMR spectra of the samples with low Al concentration are quite different from those of highly Al concentrated samples. This difference is attributed to the change of the magnetic structure of these compounds. NMR parameters calculated from the Ga NMR results are reported, too. The magnetic structures of these compounds are discussed on the basis of the Ga NMR results.

[en] Order parameters of random magnetic mixtures generally depend on the observation time. This effect causes non-equilibrium phase transition. The dynamic Monte Carlo simulation is used to analyze the phenomena and reproduces features of an experiment

[en] Jackson's group and Mito's group have performed the systematic studies for the GPa high-pressure effects on the magnetic properties of the heavy lanthanide elements. They found that the Curie temperatures decrease linearly with increasing pressure and the magnetic signals disappear at around 9.0 GPa for Gd, 7.5 GPa for Tb, 7.4 GPa for Dy and 11.0 GPa for Ho. With the Anderson's point of view, the results of our band calculation conclude that some part of the decreasing of the bulk magnetization of Gd by pressure is caused by the narrowing of the bandwidth of itinerant s, d hybridized conduction electrons and the broadening of the bandwidth of localized f-orbital electrons

[en] We present neutron diffraction results of the magnetic structure, phase transitions and magnetic short-range order of Co_1-xMn_xCl₂.2H₂O/D₂O single crystals. For samples in an intermediate composition range, where a spin glass phase exists, we found the coexistence of spin glass and long-range antiferromagnetic order. ((orig.))

[en] The NMR spectra demonstrate that the ground state of the A-site ordered manganite LaBaMn₂O₆ is the coexistent one of the ferromagnetic and antiferromagnetic domains, which are assigned to the metal and the insulating charge-ordered states, respectively. The ferromagnetic domain in LaBaMn₂O₆ is identical to the bulk ferromagnetic metal phase of the disordered La_0.5Ba_0.5MnO₃, irrespective of the absence of A-site disorder