Anisotropic spin-glass and magnetic behavior in single-crystalline U2PtSi3

The results of ac and dc susceptibilities, magnetization, magnetic relaxation, electrical resistivity, and specific heat measurements performed on a hexagonal AlB2-type single-crystalline U2PtSi3 are reported. The previously reported spin-glass transition in polycrystalline U2PtSi3 was confirmed to also occur in the single-crystalline sample with spin freezing temperature Tf=12.4 K. It is newly found that the spin-glass effect and magnetic behavior of U2PtSi3 measured along and perpendicular to the hexagonal c-axis show different magnetic field responses. Along the hard magnetization axis (c-axis), both the rate of change of Tf with the magnetic field and the detected magnetic viscosity coefficient are much smaller than those obtained in the c-plane. On the other hand, the low-temperature specific heat measurement yields an enhanced coefficient of the linear temperature term, and the temperature dependence of electrical resistivity illustrates a shallow minimum at the temperature much larger than Tf. The possible mechanisms for these phenomena are discussed by comparing with the corresponding properties observed in other ternary 2:1:3 uranium intermetallic compounds.