Low-temperature physical properties of single crystal alpha-US1.82
Résumé
We have studied a single crystal of alpha-US1.82 by measuring the magnetization M, electrical resistivity rho, magnetoresistance MR and specific heat C-p. Our experimental data establish that alpha-US1.82 is an antiferromagnet with T-N = 35 K and the easy magnetization is along the c-axis. Low-temperature properties of alpha-US1.82 are characterized also by an enhanced Sommerfeld coefficient gamma = 47 mJ/molK(2) and meta magnetic transition at mu H-0(cr) = 5.5 T. The latter behaviour accompanies with a huge MR of 52 % and abrupt collapse in the gamma(H) dependence, pointing to magnetic field-induced change of both magnetic superzone boundaries and density of states at the Fermi level. The temperature dependence of magnetic specific heat below 20 K is found to follow a function of thermally activated magnons: C-mag alpha T-exp(n)(-Delta/k(B)T), with Delta/k(B) = 3.5-6.9 K and n = 1.5-2.0. The observed exponent values seem to suggest the coexistence of ferromagnetic and antiferromagnetic interactions or two-dimensional anti ferromagnetic arrangements of magnetic uranium moments. The MR and C-p data show evidence of short-range interactions in the temperature range T-N- 2T(N), presumably caused by non-stoichiometric character of compound. The specific heat behaviour is discussed invoking the Kondo state with Kondo temperature T-K similar to 15 K and crystal electric field effect with splitting energy of 150-190 K. (C) 2016 Elsevier B.V. All rights reserved.