Structural and magnetocaloric properties of (Mn,Fe)2(P,Si) materials with added nitrogen

Amongst magnetic materials that exhibit a giant magnetocaloric effect near room temperature, the (Mn,Fe)2(P,Si) system is one of the most promising candidates for magnetic refrigeration. Although the (Mn,Fe)2(P,Si) materials hold many advantages, controlling the magnetic entropy change ΔSm, the adiabatic temperature change ΔTad, the thermal hysteresis and the mechanical stability across the ferromagnetic transition requires a delicate tuning of the composition. This work investigates the addition of nitrogen, as an interstitial or substitutional element, as a new parameter to tune the properties of (Mn,Fe)2(P,Si) materials. We found that the nitrogen addition results in a decrease of the Curie temperature, consistent with the observed increase in the c/a ratio. The introduction of nitrogen in (Mn,Fe)2(P,Si) materials also results in a strong enhancement of the mechanical stability.