Pressure Effects on Heat Capacity of the Haldane System NENP

Abstract

Heat capacity measurement has been carried out on the Haldane system NENP under the pressure P between 0 kbar-5bar^-1, where γ corresponds to the magnetic Grüneisen constant and κ_b to the compressibility along the chain axis of the NENP. No trace of three-dimensional ordering is detected in the present pressure and temperature ranges.The amplitude of magnetic heat capacity is not constant and increases roughly with increasing pressure. This behavior is considered to be due to the pressure dependence of single ion anisotropy D and interchain exchange interaction J'.