Low-temperature physical properties of single crystal α-US1.82

Abstract

We have studied a single crystal of α-US1.82 by measuring the magnetization M, electrical resistivity ρ, magnetoresistance MR and specific heat Cp. Our experimental data establish that α-US1.82 is an antiferromagnet with TN = 35 K and the easy magnetization is along the c-axis. Low-temperature properties of α-US1.82 are characterized also by an enhanced Sommerfeld coefficient γ = 47 mJ/molK2 and metamagnetic transition at μ0Hcr = 5.5 T. The latter behaviour accompanies with a huge MR of −52 % and abrupt collapse in the γ(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: Cmag∝Tnexp(−Δ/kBT), with Δ/kB = 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 antiferromagnetic arrangements of magnetic uranium moments. The MR and Cp data show evidence of short-range interactions in the temperature range TN − 2TN, presumably caused by non-stoichiometric character of compound. The specific heat behaviour is discussed invoking the Kondo state with Kondo temperature TK ∼ 15 K and crystal electric field effect with splitting energy of 150–190 K.