Crossover from one- to three-dimensional behavior in the S = 1/2 Heisenberg antiferromagnet Cu(N2H5)2(SO4)2

Abstract

From experimental and theoretical analyses of magnetic and specific-heat properties, we present the complete magnetic phase diagram of the quasi-1D antiferromagnet Cu(N2H5)2(SO4)2. On cooling and at zero magnetic field this compound enters a 1D regime with short-range magnetic correlations, marked by a broad maximum in the specific heat and magnetic susceptibility at K, followed by a tridimensional antiferromagnetically ordered phase below K induced by small interchain couplings. The intermediate-temperature 1D regime can be modeled using exact quantum-transfer-matrix calculations, which offer a compatible description of the nonmonotonic behavior of as a function of the magnetic field, giving K for the intrachain exchange parameter. The analysis of magnetic specific-heat and susceptibility data at low temperature indicates that the interchain exchange couplings are an order of magnitude smaller than the coupling inside the chains.