Magnetic, electrical and thermodynamic properties of UCuTxAl11−x alloys where T = Mn, Fe and x = 4 and 5

Abstract

The structure, magnetic, electrical, and thermodynamic properties of UCuTxAl11−x alloys, where T = Mn or Fe and x = 4 or 5 are presented. The behavior of the Fe alloys is ferromagnetic-like with the Curie points amounting to 180 and 230 K, and the saturation magnetic moments under magnetic field of 5 T equal to 4.75 and 6.02 μB/f.u., respectively, whereas under a magnetic field of about 34 T the magnetic moments amount to 6.9 and 9.0 μB/f.u. for the alloys with x = 4 and 5, respectively. The Curie points are reflected in the temperature dependence of the specific heat in which the anomalies are found at 180–200 and 230 K for alloys with x = 4 and 5, respectively, however, it shows no reflection in the temperature dependence of the electrical resistivity. The field dependence of the magnetization at T = 1.9 K for both compounds exhibits considerable hysteresis. There is a pronounced difference between ZFC and FC magnetization in its temperature dependence below the Curie point for materials with x = 4 and 5. The Mn alloys exhibit ferrimagnetic-like character for which, supposedly, the interplay of the uranium and manganize sublattices is responsible. Magnetic transitions are determined at TN = 300 (x = 4) and 380 K (x = 5). However, those anomalies do not find confirmation in the temperature dependence of the specific heat and the electrical resistivity. Magnetic moments determined at T = 1.9 K and in a magnetic field of 5 T are very low and in both cases amount to about 0.35 μB/f.u. and these values are slightly higher in a magnetic field of 34 T reaching a value of about 1.5 μB/f.u. Also for the Mn alloys the clear difference between ZFC and FC magnetization in its temperature dependence below the Curie point is observed.