Journal of the Less-Common Metals, 175 zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPO (1991) 267-270 LCM 1260 267 On magnetic transitions in a novel compound, UPdGa zyxwvutsrqponmlkji V. H. Tran and R. TroC W. Trzebiatouski Institute zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCB for Low Temperature and Structure Research, Polish Academy of Sciences, 50-950 Wroc/ aw (Poland) (Received March 19, 1991) zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDC Abstract A new ternary uranium compound, UPdGa, crystallizing in the hexagonal Fe,P-type structure has been prepared. The magnetic and electrical properties of this material have been studied in the temperature range 4.2-300 K. The results obtained indicate the appearance of two magnetic phase transitions at 30 and 62 K, probably originating from an antiferromagnetic ordering. 1. Introduction The magnetic properties of different UTGa compounds, where T is a transition metal, have been studied in numerous works [ 11. However, no such data have been published for UPdGa. In this paper we report the results of X-ray, magnetic susceptibility, magnetization (up to 14 T) and electrical resistivity measurements made on this compound. 2. Experimental details and results The samples of UPdGa were prepared by arc melting the constituent metals under a purified argon atmosphere. The resulting specimens were then annealed in an evacuated quartz tube at 600 “C for 2 weeks. Analysis of the powder X-ray diffraction pattern at room temperature has shown that UPdGa crystallizes in the hexagonal FeaP-type structure (space group P62m), as is the case for other UT(Al, Ga) compounds [ 11. The lattice parameters for UPdGa are a = 7.029 A and c = 4.113 A. Thus the U-U spacing is about 3.72 A, which is comparable to the values found for other UT(Al, Ga) phases 121. The magnetic susceptibility was measured by the Faraday method between 4.2 and 300 K in a field of 0.5 T using an RH-Cahn balance. In Fig. 1 we show the temperature dependence of the magnetic susceptibility for UPdGa. Above 100 K the susceptibility can be described by a modified Curie-Weiss law: x(T) =x0 + C/(0,-- 7’). A best fit to the experimental data yields 0, = 51 K, peff= 1.94 I,L~ and x0=0.98x 10m3 e.m.u. mol-‘. At low temperatures 0022-5088/91/$3.50 0 1991 - Elsevier Sequoia, Lausanne