Akira Oosawa

Observation of Field-Induced Transverse Neel Ordering in the Spin Gap System TlCuCl3.

Neutron elastic scattering experiments have been performed on the spin gap system TlCuCl 3 in magnetic fields parallel to the b -axis. The magnetic Bragg peaks which indicate the field-induced Neel ordering were observed for the magnetic field higher than the gap field H g ≈5.5 T at Q =( h , 0, l ) with odd l in the a * - c * plane. The spin structure in the ordered phase was determined. The temperature and field dependence of the Bragg peak intensities and the phase boundary obtained were discussed in connection with a recent theory which describes the field-induced Neel ordering as a Bose-Einstein condensation of magnons.

Neutron Diffraction Study of the Pressure-Induced Magnetic Ordering in the Spin Gap System TlCuCl3

Neutron elastic scattering measurements have been performed under a hydrostatic pressure in order to investigate the spin structure of the pressure-induced magnetic ordering in the spin gap system TlCuCl 3 . Below the ordering temperature T N =16.9 K for the hydrostatic pressure P =1.48 GPa, magnetic Bragg reflections were observed at reciprocal lattice points Q =( h , 0, l ) with integer h and odd l , which are equivalent to those points with the lowest magnetic excitation energy at ambient pressure. This indicates that the spin gap closes due to the applied pressure. The spin structure of the pressure-induced magnetic ordered state for P =1.48 GPa was determined.

Microscopic Phase Separation in Triangular-Lattice Quantum Spin Magnet κ-(BEDT-TTF)2Cu2(CN)3 Probed by Muon Spin Relaxation

The ground state of the quantum spin system κ-(BEDT-TTF) 2 Cu 2 (CN) 3 , in which antiferromagnetically interacting S =1/2 spins are located on a nearly equilateral triangular lattice, attracts con...

Pressure-Induced Magnetic Quantum Phase Transition in Gapped Spin System KCuCl3

Magnetization and neutron elastic scattering measurements under a hydrostatic pressure were performed on KCuCl 3 , which is a three-dimensionally coupled spin dimer system with a gapped ground state. It was found that an intradimer interaction decreases with increasing pressure, while the sum of interdimer interactions increases. This leads to the shrinkage of spin gap. A quantum phase transition from a gapped state to an antiferromagnetic state occurs at P c ≈8.2 kbar. For P > P c , magnetic Bragg reflections were observed at reciprocal lattice points equivalent to those for the lowest magnetic excitation at zero pressure. This confirms that the spin gap decreases and closes under applied pressure.

Magnetic field induced one-magnon Raman scattering in the magnon Bose-Einstein condensation phase of TlCuCl 3

We report the observation of the

1H-NMR Study on the Magnetic Order in the Mixture of Two Spin Gap Systems (CH3)2CHNH3CuCl3 and (CH3)2CHNH3CuBr3

A_{\rm g}

Field-Induced Two-Step Phase Transitions in the Singlet Ground State Triangular Antiferromagnet CsFeBr3

-symmetric one-magnon Raman peak in the magnon Bose-Einstein condensation phase of TlCuCl

Muon spin relaxation detection of the soft mode toward the exotic magnetic ground state in the bond-disordered quantum spin system IPA-Cu(Cl0.35Br0.65)3

_{3}

Partial Disordered Phase of Ising Spin System in Distorted Triangular Lattice RbCoBr3

. Its Raman shift traces the one-magnon energy at the magnetic

One-Magnon Raman Scattering as a Probe of Longitudinal Excitation Mode in Spin Dimer Systems

\Gamma