Unusual signatures of the ferromagnetic transition in the heavy fermion compound UMn_2Al_(20)

摘要

Magnetic-susceptibility results for single crystals of the new cubic compounds UT_2Al_(20) (r=Mn, V, and Mo) are reported. Magnetization, specific-heat, resistivity, and neutron-diffraction results for a single crystal and neutron diffraction and inelastic spectra for a powder sample are reported for UMn_2Al_2o-.For T=V and Mo, temperature-independent Pauli paramagnetism is observed. For UMn_2Al_(20), a ferromagnetic transition is observed in the magnetic susceptibility at T_c=20 K. The specific-heat anomaly at T_c is very weak while no anomaly in the resistivity is seen at T_c. We discuss two possible origins for this behavior of UMn_2Al_(20): moderately small moment itinerant ferromagnetism or induced local-moment ferromagnetism.