THE LOW-TEMPERATURE PHASE-DIAGRAM OF UCU5 DETERMINED FROM MAGNETIZATION AND MAGNETORESISTANCE MEASUREMENTS

The low-temperature phase diagram of polycrystalline UCu5 has been determined from magnetization and magnetoresistance measurements. This system undergoes two magnetic transitions at low temperatures. The lower-temperature phase transition at T-2 = 1.16 K, which manifests itself as a sudden jump in the magnetization and electrical resistance with decreasing temperature, shows a temperature hysteresis of about 40 mK for fields up to 12 T. The magnetic properties of this low-temperature phase show irreversible and metastable behaviour, which becomes more dramatic at the lower fields. The critical temperature T-2 is observed to increase proportionally with the square of the magnetic field. Our results are discussed in comparison with available specific heat, neutron scattering and nuclear magnetic resonance data, with the aim of determining the actual nature of the low-temperature magnetic phase transition.