Magnetic refrigeration is currently gaining an increasing interest due to the discovery of materials with remarkable magnetocaloric response close to room temperature. Among others, the main advantages of the refrigerators based on the magnetocaloric effect (MCE) with respect to the systems based on the compression-expansion gas cycle are an improvement in the energetic efficiency and the avoidance of ozone depleting and green-house effect gasses. The characterization of the magnetocaloric materials is based on two parameters: the peak of the magnetic entropy change (ΔS_M^pk) and the refrigerant capacity (RC). The study of amorphous materials for use in magnetic refrigeration has been motivated by finding a compromise between the aforementioned parameters: a modest ΔS_M^pk with a high RC. These quantities together with their reduced magnetic and thermal hysteresis, high electrical resistivity, acceptable mechanical properties and corrosion resistance make them good candidates as magnetic refrigerators. The aim of this work is to study the influence of the manganese content on the magnetocaloric response of the Fe_80-xMn_xB₂₀ alloy series (x = 10, 15, 18, 20 and 24). The magnetic entropy change has been calculated from the numerical derivative of the magnetization curves with respect to temperature and subsequent integration in field, and the RC have been obtained from the product of ΔS_M^pk times the full temperature width at half maximum of the peak (RC_FWHM). The results indicate a nearly linear dependence on the manganese content of the Curie temperature Tc, the maximum magnetic entropy change ΔS_M^pk, and the magnetic refrigeration RC_FWHM, with slopes of -20 K/at. % Mn, -0.04 J·K^-1·kg^-1/at. % Mn and ‑3.5 J·kg^‑1/at. % Mn, respectively.

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