The (Mn,Fe)₂(P,Si) compounds with large magnetocaloric effect are sensitive to the contents of impurity phase. In order to decrease its contents, the (MnFe)_δ(P_0.5Si_0.5) (δ = 1.90, 1.95, 2.00, 2.05) compounds were designed and prepared by arc-melting method. The structure and magnetic properties were characterized by XRD, SEM, DSC and VSM, respectively. The diffraction analysis reveals that all samples are hexagonal Fe₂P-type crystals with some impurity phase. The structure of impurity phase would change from cubic (Mn,Fe)₃Si to hexagonal (Mn,Fe)₅Si₃ with decreasing δ from 2.05 to 1.90. And the Curie temperature of (MnFe)_δ(P_0.5Si_0.5) compounds increased from 234 K for δ = 2.05 to 371 K for δ = 1.90. Meanwhile, the thermal hysteresis decreased by 58%. Under the field change of 5 T, the peak values of isothermal entropy change reaches 19.6 J‧kg⁻¹‧K⁻¹ for δ = 1.95. While, the maximal adiabatic temperature change increased by 47% as δ decreasing from 2.05 to 1.90. All results show that the impurity phase and magnetic properties of the (Mn,Fe)₂(P,Si) compounds can be effectively tuned by adjusting M/NM ratios.

磁热效应大的（Mn，Fe）₂（P，Si）化合物对杂质相的含量敏感。为了降低其含量，设计并通过电弧熔融法制备了（MnFe）_δ（P _0.5 Si _0.5）（δ＝ 1.90、1.95、2.00、2.05）化合物。分别用XRD，SEM，DSC和VSM表征了结构和磁性能。衍射分析表明，所有样品均为具有某些杂质相的六角形Fe ₂ P型晶体。杂质相的结构将从立方（Mn，Fe）₃ Si变为六方形（Mn，Fe）₅ Si ₃，其δ从2.05降低到1.90。居里温度为（MnFe）_δ（P _0.5 Si _0.5）化合物从δ= 2.05的234 K增加到δ= 1.90的371K。同时，热滞降低了58％。在5 T的磁场变化下，δ= 1.95时，等温熵变的峰值达到19.6 J·kg ^-1· K ^-1。同时，随着δ从2.05降低到1.90，最大绝热温度变化增加了47％。所有结果表明，通过调节M / NM比可以有效地调节（Mn，Fe）₂（P，Si）化合物的杂质相和磁性。