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

The low-temperature phase diagram of polycrystalline UCu5 has been det ermined from magnetization and magnetoresistance measurements. This sy stem 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 d ecreasing temperature, shows a temperature hysteresis of about 40 mK f or fields up to 12 T. The magnetic properties of this low-temperature phase show irreversible and metastable behaviour, which becomes more d ramatic 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, neut ron scattering and nuclear magnetic resonance data, with the aim of de termining the actual nature of the low-temperature magnetic phase tran sition.