THERMAL-EXPANSION OF CEPDSB NEAR THE FERROMAGNETIC TRANSITION

The thermal expansion of CePdSb has been measured between 1.6 and 30 K in magnetic fields of up to 8 T. The magnetic contribution to the lin ear thermal-expansion coefficient of polycrystalline CePdSb (alpha(p)) in zero magnetic field has a maximum value near 10 K and becomes smal l by 20 K. There is no peak in alpha(p) at the Curie point, T-C=17 K. This anomalous behavior is in agreement with earlier heat-capacity mea surements. The maximum value of ct, decreases in a magnetic field and moves to a higher temperature. The thermal expansion of a single cryst al of CePdSb was found to be highly anisotropic. In the magnetically h ard c direction the thermal-expansion coefficient (alpha(c)) has a max imum value near 10 K some three times larger than that of the peak in alpha(p). The value of alpha(c) is negative above T-C and then shows t he beginnings of a normal critical response near T-C before being subm erged in the broad 10 K peak. The values of alpha(a) (alpha(b)) are sm all in magnitude and negative (positive) below 14 K in zero field but both become positive in a field of 8 T. The strong secondary peak in t he ac susceptibility of CePdSb reported earlier, some 11 K below T-C, was observed in samples prepared by are melting but not in those produ ced in sealed crucibles and is therefore probably due to material with a deficiency of Sb.