ELASTIC EFFECTS IN SOME FERROMAGNETIC URANIUM PNICTIDES

Abstract

The results of ultrasonic velocity measurements on single-crystalline U 3 P 4, UCuP 2 and UCuAs 2 ferromagnets are presented. For cubic U 3 P 4 the temperature dependence of all three non-zero elastic constants c 11, c 12 and c 44 has been derived. All of them exhibit a strong softening In the vicinity of T C but particularly large effect (~13%) is observed in the case of the shear constant c 12. For tetragonal UCuP 2 and UCuAs 2 the sound propagation along the c-axis has only been studied. In UCuP 2 both the c 33 and c 44 constants show a strong softening near the magnetic phase transition (~ 7%). Much smaller anomalies in elastic constants at T C and an unusual temperature dependence of c 44 In the ferromagnetic region are observed for the arsenide.