Magnetic Phase Transitions in U3Al2Si3

Abstract

Magnetic phase transitions to magnetic ordered state have been investigated on a U3Al2Si3 textured sample by measurements of electrical resistivity, magnetization and specific heat in the temperature range 2 – 70 K for magnetic field up to 14 T. The magnetic measurements confirmed a magnetic ordering at Tc ≈ 40 K but on contrary to previous reports we have observed a remarkable magnetic anisotropy of the easy plane type with magnetization Me0=1.6μB/f.u. extrapolated to zero field for magnetic easy axis and Mho= 0.2μB/f.u. for hard axis. The magnetic phase transition is accompanied by broad anomalies in resistivity and heat capacity data. The applied magnetic field smears out the maximum in resistivity at T = 26 K and the maximum in specific heat at T = 36 K as well as shifts them to higher temperatures. Magnetic contribution to specific heat Cmag has maximum at the ordering temperature Tc = 39 K and surprisingly it is non-zero up to about 100 K well above Tc. The magnetic entropy saturates to value 35 J/mol K that is close to 3 R ln 4. Around the ordering temperature Tc the entropy is about 3 R ln 2. There is a surplus of the specific heat above Tc and an anomaly in magnetization at 60 K that is induced by the magnetic field. It could be an evidence of some kind of order that has not been observed yet.