Giant magnetocaloric effect and hysteresis loss in MnxFe2-xP0.5Si0.5 (0.7 ≤ x ≤ 1.2) microwires at ambient temperatures

Magnetocaloric microwires are very promising for energy-efficient magnetic refrigeration in micro electromechanical systems (MEMS) and nano electromechanical systems (NEMS). Creating microwires that exhibit large magnetocaloric effects around room temperature represents an important but challenging task. Here, we report a tunable giant magnetocaloric effect around room temperature in Mn_xFe_2-xP_0.5Si_0.5 (0.7≤x ≤ 1.2) microwires by utilizing a melt-extraction technique paired with thermal treatment and chemical engineering. The isothermal magnetic entropy change (ΔS_iso) and Curie temperature (T_C) can be tuned by adjusting the Mn/Fe ratio. The T_C varies from 351 to 190 K as x increases from 0.8 to 1.2. Among the compositions investigated, the x = 0.9 sample shows the largest value of ΔS_iso = 18.3 J kg⁻¹ K⁻¹ for a field change of 5 T around 300 K. After subtracting magnetic hysteresis loss, a large refrigerant capacity of ∼284.6 J kg⁻¹ is achieved. Our study paves a new pathway for the design of novel magnetocaloric microwires for active magnetic refrigeration at ambient temperatures.