Magnetic lock-in phase transition in Tb0.95Er0.05Ni5 driven by low magnetic fields

The magnetic properties of a mixed inter-metallic compound, Tb0.95Er0.05Ni5, were investigated using a neutron diffraction method at low temperatures. These compounds were known to have a successive magnetic phase transition from the paramagnetic state at high temperature to a lock-in phase at low temperature through intermediate phases, i.e., PM(paramagnetic)-FM(ferromagnetic)-IC(incommensurate)-L(lock-in) in reverse order of temperature. A meta-magnetic phase transition between an IC phase and a FM phase at 9 K was observed with the critical field, HMT~200 mT. A new magnetic phase between the new phase (lock-in phase) and an IC phase has been observed. From the field dependence of the Bragg reflections and their satellite peaks at low temperatures (3-12 K), weak field driven first-order magnetic phase transitions were recorded at six fixed temperatures. The critical magnetic field decreases exponentially with the temperature. From these experimental results, we obtained a magnetic phase diagram of Tb0.95Er0.05Ni5 at a low temperature region for the first time.