Magnetic anisotropy and spin-glass behavior in single crystalline U2PdSi3

We present the magnetic and transport properties of single crystalline U(2)PdSi(3) measured with the magnetic field (H) (or measuring current, I) applied along two typical crystallographic directions, i.e. H ⊥ c-axis and H c-axis (or I ⊥ c-axis and I c-axis). For both directions, a spin-glass state is confirmed to form at low temperature with the same spin freezing temperature T(f) (=11.5 K), initial frequency shift δT(f) (=0.023) and activation energy E(a)/k(B) (=90.15 K) in zero dc field. Strong anisotropy in magnetic and transport behavior is found to be a significant feature of U(2)PdSi(3). The unusual ferromagnetic-like anomaly in ac susceptibility and dc magnetization curves around T(m)=71 K is observed in the case of H c-axis but not in the cases of H ⊥ c-axis. The characteristic temperature T(ir), below which evident irreversible magnetism originated from random spin freezing can be observed, shows much stronger field dependence for H ⊥ c-axis than for H c-axis. Moreover, an unusual finding is that the electrical resistivity measurements indicate the formation of magnetic Brillouin-zone boundary gaps and much larger magnetic scattering for I ⊥ c-axis, while the coherent-Kondo-effect-like behavior is obvious for I c-axis. We also emphasize that no resistivity minimum can be detected down to 2.5 K for either direction. The observed magnetic and transport behaviors are compared with those in polycrystalline U(2)PdSi(3) and other 2:1:3 intermetallic compounds.