Magnetic state in URu2Si2, UPd2Al3, and UNi2Al3 probed by point contacts

The antiferromagnetic (AFM) state is investigated in the three heavy-fermio n compounds URu2Si2, UPd2Al3, and UNi2Al3 by measuring dV/dI(V) curves of p oint contacts at different temperatures 1.5-20 K and magnetic fields 0-28 T . The zero-bias maximum in dV/dI(V) for URu2Si2 points to a partially gappe d Fermi surface related to the itinerant nature of the AFM state, contrary to the case of UPd2Al3, where analogous features have not been found. The A FM state in UNi2Al3 has more similarities with URu2Si2. For URu2Si2, the sa me critical field of about 40 T along the easy axis c is found for all feat ures in dV/dI(V), corresponding to the Neel temperature, the gap in the ele ctronic density of states, and presumably the ordered moments. (C) 2001 Ame rican Institute of Physics.