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

Abstract

Neutron elastic scattering measurements have been performed under the\nhydrostatic pressure in order to investigate the spin structure of the\npressure-induced magnetic ordering in the spin gap system TlCuCl$_3$. Below the\nordering temperature $T_{\\rm N}=16.9$ K for the hydrostatic pressure $P=1.48$\nGPa, magnetic Bragg reflections were observed at the reciprocal lattice points\n${\\mib Q}=(h, 0, l)$ with integer $h$ and odd $l$, which are equivalent to\nthose points with the lowest magnetic excitation energy at ambient pressure.\nThis indicates that the spin gap closes due to the applied pressure. The spin\nstructure of the pressure-induced magnetic ordered state for $P=1.48$ GPa was\ndetermined.\n