KEr(MoO4)(2): A quasi-one-dimensional S=(3)/(2) Blume-Capel system

In paper we present experimental data and Monte Carlo calculations of KEr(M oO4)(2) specific heat in the temperature range 0.4-6 K and in magnetic fiel d B from 0-1 T applied along the easy axis. The data analysis for B = 0 has identified KEr(MoO4)(2) as an S = 3/2 Blume-Capel model on rectangular lat tice with the intrachain exchange interaction (J) over tilde(1)/k(B) = 0.38 K, interchain exchange interaction (J) over tilde(2)/k(B) = - 0.07 K, and single-ion anisotropy D/k(B) = 10 K, with the ordering temperature T-c = 0. 95 K. Further Monte Carlo studies of the Blume-Capel model in the magnetic field applied along the easy axis have been focused on the formation of clu ster excitations in a paramagnetic regime. The magnetic-field dependence of a cluster mean length studied in the chain direction exactly follows the b ehavior of S = 1/2 Ising chain at least for the given set of (J) over tilde (1), (J) over tilde(2). and D parameters. On the other hand, the specific h eat in nonzero field represents a more sensitive quantity to the presence o f interchain correlations and the occupation of a higher doublet.