Spin-glass behaviour of novel ternary uranium aluminide U₃Co_4+xAl_12−x (x = 0.55)

Abstract

Experimental results on dc and ac susceptibility, magnetization and magnetic relaxation, specific heat, electrical resistivity and magnetoresistivity up to 8 T are reported for the novel ternary uranium aluminide U₃Co_4.55Al_11.45. The temperature dependence of the dc susceptibility shows a cusp at a characteristic temperature T _f = 8–10 K that depends weakly on the applied magnetic field. The observed pronounced difference between the ZFC and FC magnetizations, as well as the decay in the remanent, both give evidence that a highly irreversible, frozen state is formed below T _f which is reminiscent of spin-glass behaviour. The real and imaginary parts of the ac susceptibility show that the corresponding T _f peaks are only slightly dependent on frequency. Electrical resistivity measured at zero and in fields up to 8 T indicates that the Kondo-like state becomes dominant at temperatures above T _f.

Acknowledgements

The authors acknowledge the help of Dr. Hab. V.H. Tran in fitting procedures made in this paper, Mrs. M. Sołyga for specific heat measurements and the technical assistance of Mr. D. Badurski and Mr. R. Gorzelniak.