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 AlB ₂-type single-crystalline U ₂PtSi ₃ are reported. The previously reported spin-glass transition in polycrystalline U ₂PtSi ₃ was confirmed to also occur in the single-crystalline sample with spin freezing temperature T f =12.4 K. It is newly found that the spin-glass effect and magnetic behavior of U ₂PtSi ₃ 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 T f 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 T f . The possible mechanisms for these phenomena are discussed by comparing with the corresponding properties observed in other ternary 2:1:3 uranium intermetallic compounds.