Critical behaviour of the magnetic susceptibility at marginal dimensionality in LiTbF4

Abstract

The parallel susceptibility of LiTbF4 has been measured in the critical region and is well described by the law chi c(t)= Gamma t-1 mod ln(t0/t) mod 1/3 where t is the reduced temperature; t=T/Tc-1 over the range 2*10-4<t<1.1*10-1 with Tc=2.8850K, Gamma =(3.87+or-0.05)*10-2 emu cgs g-1, t0=5.5+or-2.5 ( Gamma N=0.910+or-0.012 in dimensionless units). A detailed discussion for the choice of t0 and of the exponent of the logarithmic correction z=1/3 is given. The universal ratio Rc between the critical amplitudes of the magnetic susceptibility, the specific heat and the spontaneous magnetisation, Rc=TcAB-2 Gamma , is tested.