Excitations in spin chains and specific-heat anomalies in Yb ₄ As ₃

Abstract

An explanation is given for the observed magnetic-field dependence of the\nlow-temperature specific heat coefficient of Yb(4)As(3). It is based on a\nrecently developed model for that material which can explain the observed\nheavy-fermion behaviour. According to it the Yb(3+)-ions are positioned in a\nnet of parallel chains with an effective spin coupling of the order of J = 25\nK. The magnetic-field dependence can be understood by including a weak magnetic\ncoupling J' between adjacent chains. The data require a ratio J'/J of about\n10^{-4}. In that case the experimental results can be reproduced very well by\nthe theory.\n