L. Asch, G. M. Kalvius, A. Kratzer
EPL (Europhysics Letters)
Para- and antiferromagnetic UAs was studied by μSR. Already 50 K above TN = 124 K the formation of a magnetic precursor phase is observed. In the type-I, 1k structure all field contributions from surrounding ordered uranium moments cancel on the average. The remaining very narrow (∼ 10 G wide) distribution of internal field is of static nature (1/τ < 0.2 MHz) proving that spin excitations (at zero energy transfer) are absent. Hence UAs has some itinerant character. In the type-IA, 2k phase the interstitial site occupied by the muon separates into three subsites. This is only possible if a distortion of the cubic lattice occurs. Such a distortion has been suggested but our μSR data give the first experimental evidence for its presence.