Influence of interchain-coupling effects on the low-T properties of the one-dimensional S=1/2 Heisenberg antiferromagnet Yb₄As₃

We have investigated the difference in the low-T specific heat, C(T, B), of single- and multi-domain Yb4As3 crystals in magnetic fields Bless than or equal to4 T. Upon increasing field, which was applied parallel to the trigonal axis, the C(T)/T values of the single-domain sample have been found to be less reduced than that of the multi-domain one. Furthermore, a minimum value of C(T)/T which is unaffected at Bgreater than or equal to1 T is observed for the single-domain sample around 0.25 K. This behavior cannot be explained by the S = 1/2; Heisenberg antiferromagnet with the intrachain coupling determined by the inelastic neutron scattering. The interchain coupling appears to be responsible for the reported C(T)/T behavior below 1 K. (C) 2002 Elsevier Science B.V. All rights reserved