Effect of Phase Transition Type on the Magnetocaloric Effect and Magnetic Hysteresis in Er(Co_1-xMn_x)₂ Laves Alloys

As magnetic refrigerants, first-order transition (FOT) and second-order transition (SOT) materials possess distinct advantages and disadvantages. If the phase transition can be tuned to the critical point between FOT and SOT, it may be possible to combine the benefits of both, thereby achieving an outstanding magnetocaloric effect. Here, we demonstrated this approach through phase transition engineering in Er(Co_1-xMn_x)₂ alloys. When x ≤ 0.06, the magnetic phase transition of the samples was FOT, exhibiting a significant magnetic entropy change. However, at x = 0.08, the samples underwent a SOT from ferromagnetic to paramagnetic, leading to a substantial reduction in the magnetocaloric effect. At the critical point of the FOT/SOT border with x = 0.06, the sample exhibited a large magnetic entropy change along with negligible magnetic hysteresis. This work demonstrates that the critical point between FOT and SOT is an effective means of achieving an excellent magnetocaloric effect.