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Bulk Mn_(1.2)Fe_(0.8)P_(0.76)Ge_(0.24) alloy was prepared by mechanical milling and subsequent spark plasma sintering technique.Effect of annealing on the structure and magneto-caloric properties of the alloy was investigated.XRD results show that both sintered and annealed samples possess a hexagonal Fe_2P-type crystal structure.After annealing,ferromagnetic impurity Fe_3Mn_4Ge_6,which exists in the sintered sample,was eliminated from the alloy.Furthermore,the lattice constants a and c change noticeably,leading to a decrease in c/a ratio,while the cell volume almost remains invariable.As a result,the Curie temperature of the alloy increases from 253 K to 298 K,but the maximum magnetic entropy change decreases from 37.5 to 11.7 J·kg·K~(-1) for 2 T magnetic field change.On the other hand,the thermal hysteresis of M-T curves around T_C upon heating and cooling is 14 and 8 K for the as-sintered and the annealed sample,respectively,showing evident change.
Bulk Mn_ (1.2) Fe_ (0.8) P_ (0.76) Ge_ (0.24) alloy was prepared by mechanical milling and subsequent spark plasma sintering technique. Effect of annealing on the structure and magneto-caloric properties of the alloy was investigated. XRD results show that both sintered and annealed samples possess a hexagonal Fe 2 P -type crystal structure. After annealing, ferromagnetic impurity Fe_3Mn_4Ge_6, which exists in the sintered sample, was eliminated from the alloy. Still more, the lattice constants a and c change noticeably, leading to a decrease in c / a ratio, while the cell volume almost remains invariable. As a result, the Curie temperature of the alloy increases from 253 K to 298 K, but the maximum magnetic entropy change decreases from 37.5 to 11.7 J · kg · K -1) for 2 T magnetic field change. On the other hand, the thermal hysteresis of MT curves around T_C upon heating and cooling is 14 and 8 K for the as-sintered and annealed sample, respectively, showing evident change.