The Magnetic Properties of Cobalt N-Butyl Phosphinate: Weak Ferromagnetism in One Dimension.

This thesis concerns the magnetic interactions in the polymeric compound cobalt n-butyl phosphinate (CoBP). The static susceptibility of powder samples of CoBP was measured by a Faraday balance from 3 to 300K, the AC susceptibility on oriented single crystal samples was measured by an AC bridge for f = 25Hz to 490 kHz, H = 0 to 40 kG and t = 1 to 5K, and electron spin resonance was observed on oriented single crystals of cobalt-doped zinc n-butyl phosphinate (Co in ZnBP). The high temperature susceptibility of CoBP is characteristic of a 1-D antiferromagnet, exchange J/k = 6K, but below 10K a ferromagnetic-like component appears. The anisotropy field and temperature dependence suggests an antisymmetric exchange d(.)s(,1) x s(,2) of strength 0.5K. The ESR data suggests a D and E anisotropy of similar strength. An anomalous absorption in zero static field appears in the AC susceptibility at low temperature. The anomaly is suppressed by a static field of 10kG; the onset temperature shows a weak frequency dependence. A correlated cluster model is discussed which explains the qualitative features of the data; soliton motion is suggested as a possible mechanism for the anomalous power absorption.