EFFECT OF PRESSURE ON THE CURIE-TEMPERATURE OF SINGLE-CRYSTAL UGE2

The linear thermal expansion of single-crystal UGe2 has been measured in the temperature range 4.2 K<T<300 K under high pressure up to 20 kb ar. The linear thermal expansion coefficient alpha(i) (K-1) (i=a, b an d c) exhibits a discontinuity near 50 K and a large anisotropy, which corresponds to ferromagnetic order. The discontinuous changes in the v alues of alpha(a), alpha(b), and alpha(c) at T-C are 25 X 10(-6) K-1, 40X10(-6) K-1 and -10x10(-6) K-1 respectively. It is found that T-C de creases with increasing pressure and becomes lower than 4.2 K at 20 kb ar. The initial decreasing rate of T-C was estimated to be dT(C)/dP= - 0.7 K kbar(-1). The data are analysed briefly by assuming a weak ferro magnetic theory.