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

We use magnetic susceptibility and inelastic neutron scattering measurements to show that copper benzoate, Cu(C6D5COO)(2) . 3D(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 held shows only the response of a S=1/2 chain. The dynamic correlation function S((q) over tilde,omega) measured by neutron scattering shows only 1D spin correlations for (h) over bar omega greater than or equal to 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.