Resistivity Studies on UM2Si2 (M = Rh, Ir, Ru and Os)

Abstract

Uranium compounds UM2Si2 (M = 3d, 4d and 5d transition metal atom) crystallizing in BaAl4-related structures, exhibit interesting magnetic properties. Depending upon the degree of hybridization with the neighbouring transition metal atoms, U-derived 5f-electrons can either be localized itinerant. A general trend in the variation of their magnetic behaviour was suggested to be emerging from the magnetic susceptibility measurements of a number of UM2Si2 systems [1]. Pauliparamagnetism via antiferromagnetism to canted antiferromagnetism with the increasing number of d electrons was suggested. For instance, Pauliparamagnetic behaviour has been reported in URe2Si2 and UOs2Si2; antiferromagnetism in UIr2Si2 and UPt2Si2; and canted antiferromagnetism in UAu2Si2. Similarly antiferromagnetism has been reported in URu2Si2, URh2Si2 and UPd2Si2 with a ferromagnetic component developing in the latter two at low temperatures. In a very recent paper on the magnetic behaviour of a large number of UM2Si2 systems, contrary results have been reported on UOs2Si2 and URh2Si2 viz., the occurrence of a weak ferromagnetic transition (Tc= 28K) in UOs2Si2 and coexistance of itinerant ferromagnetism with Tc = 16K and a localized antiferromagnetism with TN = 131K [2]. The aim of the present work, in view of the above mentioned contradictory results, was to re-examine the magnetic behaviour of four members of this class of U-based systems, namely, UM2Si2 (M = Ru, Rh, Os and Ir).