MAGNETIC-PROPERTIES OF A QUASI-ONE-DIMENSIONAL S=1 2 ANTIFERROMAGNET - COPPER BENZOATE/

We use magnetic susceptibility and inelastic neutron scattering measur ements to show that copper benzoate, Cu(C6D5COO)(2) . 3D(2)O, is a qua si-one-dimensional S=1/2 antiferromagnet with an exchange constant J=1 .57 meV Below T=0.8 K a ferromagnetic contribution to the susceptibili ty marks the onset of canted three-dimensional (3D) antiferromagnetic order. An external magnetic held suppresses this effect, and the susce ptibility measured in high held shows only the response of a S=1/2 cha in. 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 evi dence of a continuum of magnetic excitations, consistent with the curr ent theoretical picture of the excitation spectrum of the S=1/2 chain at T=0 K.