title: 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 [Formula: see text] K, followed by a tridimensional antiferromagnetically ordered phase below [Formula: see text] 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 [Formula: see text] as a function of the magnetic field, giving [Formula: see text] 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.
authors: Instituto de Física, Universidade de São Paulo, 05314-970 São Paulo, Brazil.
authors: A
authors: A
authors: Paduan-Filho
authors: A P
authors: AP
authors: Vieira
authors: J G A
authors: JG
authors: Ramon
authors: R S
authors: RS
authors: Freitas