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First-order ferromagnetic transition in single-crystalline (Mn,Fe)2(P,Si)

(Mn,Fe)2(P,Si) single crystals have been successfully grown by flux method. Single crystal diffraction demonstrates that Mn0.83Fe1.17P0.72Si0.28 crystallizes in a hexagonal crystal structure (space group P-62m) at both 100 and 280 K, in the ferromagnetic and paramagnetic states, respectively. The magnetization measurements show that the crystals display a first-order ferromagnetic phase transition at their Curie temperature (TC). The preferred magnetization direction in is along the c axis. A weak magnetic anisotropy of K1 = 0.25x106 J/m3 and K2 = 0.19x106 J/m3 is found at 5 K. These values indicate a soft magnetic behaviour favourable for magnetic refrigeration. A series of discontinuous magnetization jumps is observed far below TC by increasing the field at a constant temperature. These magnetization jumps are irreversible, occur spontaneously at constant temperature and magnetic field, but can be restored by cycling across the first-order phase transition.