Search for magnetocrystalline anisotropy in U3M2M '(3)

Magnetic properties of novel ferromagnetic compounds U3Al2M'(3) (M'= Ge or Si) have been studied on single crystalline specimens. Hysteresis loop meas urements confirm that crystallographic c-axis is magnetic hard axis. The co ercive force in the case of c-axis ( B-c = 0.178 T or B-c = 0.255 T) is onl y a little bit higher than in the case of b-axis (B-c = 0.173 T or B-c = 0. 190 T) for U3Al2Ge3 or U3Al2Si3, respectively, but losses given by the area of hysteresis loop are remarkably larger for c-axis. Susceptibility measur ements suggest that there is a very small magnetocrystalline anisotropy bet ween b-axis and c-axis. U3Al2Ge3 becomes ferromagnetic below 65 K. The Curi e-Weiss law is very well fulfilled for b- and c-axis in temperature range 8 0 K - 300 K (Theta = 67K and mu(eff) = 1.68 mu(B)/at.U). In the case of U3A l2Si3 the Curie temperature is 32 K and the susceptibility data fit the mod ified Curie-Weiss law (chi o = 5.4 x 10(-8) m(3)/mole, Theta = 29 K and mu( eff) = 0.69 mu(B)/U-atom).