First-order ferromagnetic transition in single-crystalline (Mn,Fe)_2(P,Si)

摘要

(Mn,Fe)_2(P,Si) single crystals have been grown by flux method. Single crystal X-ray diffraction demonstrates that Mn_(0.83)Fe_(1.17)P_(0.72)Si_(0.28) crystallizes in a hexagonal Fe_2P crystal structure (space group P62m) at both 100 and 280 K, in the ferromagnetic and paramagnetic states, respectively. Magnetization measurements show that the crystals display a first-order ferromagnetic phase transition at their Curie temperature (T_C). The preferred magnetization direction is along the c axis. A weak magnetic anisotropy of K_1 =0.28 × 10~6 J/m~3 and K_2 = 0.22 × 10~6J/m~3 is found at 5K. A series of discontinuous magnetization jumps is observed far below T_C by increasing the field at constant temperature. These magnetization jumps are irreversible, occur spontaneously at a constant temperature and magnetic field, but can be restored by cycling across the first-order phase transition.