Magnetic Phase Diagram of the Mn(x)Fe(2−x)P(1−y)Si(y) System

The phase diagram of the magnetocaloric Mn(x)Fe(2−x)P(1−y)Si(y) quaternary compounds was established by characterising the structure, thermal and magnetic properties in a wide range of compositions (for a Mn fraction of 0.3 ≤ x < 2.0 and a Si fraction of 0.33 ≤ y ≤ 0.60). The highest ferromagnetic transition temperature (Mn(0.3)Fe(1.7)P(0.6)Si(0.4), T(C) = 470 K) is found for low Mn and high Si contents, while the lowest is found for low Fe and Si contents (Mn(1.7)Fe(0.3)P(0.6)Si(0.4), T(C) = 65 K) in the Mn(x)Fe(2−x)P(1−y)Si(y) phase diagram. The largest hysteresis (91 K) was observed for a metal ratio close to Fe:Mn = 1:1 (corresponding to x = 0.9, y = 0.33). Both Mn-rich with high Si and Fe-rich samples with low Si concentration were found to show low hysteresis (≤2 K). These compositions with a low hysteresis form promising candidate materials for thermomagnetic applications.