Magnetic properties of a quasi-one-dimensional S=1/2 antiferromagnet: Copper benzoate.

Abstract

We use magnetic susceptibility and inelastic neutron scattering measurements to show that copper benzoate, Cu(${\mathrm{C}}_{6}$${\mathrm{D}}_{5}$COO${)}_{2}$\ensuremath{\cdot}${3\mathrm{D}}_{2}$O, is a quasi-one-dimensional S=1/2 antiferromagnet with an exchange constant J = 1.57 meV. Below T=0.8 K a ferromagnetic contribution to the susceptibility marks the onset of canted three-dimensional (3D) antiferromagnetic order. An external magnetic field suppresses this effect, and the susceptibility measured in high field shows only the response of a S=1/2 chain. The dynamic correlation function S(q\ifmmode \tilde{}\else \~{}\fi{},\ensuremath{\omega}) measured by neutron scattering shows only 1D spin correlations for \ensuremath{\Elzxh}\ensuremath{\omega}\ensuremath{\ge}0.4 meV at T = 1.8 K. There is clear evidence of a continuum of magnetic excitations, consistent with the current theoretical picture of the excitation spectrum of the S=1/2 chain at T = 0 K. \textcopyright{} 1996 The American Physical Society.