A Comparative Study of the Magnetocaloric Effect in MnFePSiGeB Prepared by Traditional Sintering and Spark Plasma Sintering

Abstract

Two compounds with the same composition of Mn <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1.15</sub> Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.85</sub> P <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.65</sub> Si <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.13</sub> Ge <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.2</sub> B <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.02</sub> have been synthesized by traditional sintering (TS) and spark plasma sintering (SPS) methods. A comparative study on the structural and magnetic properties of the compounds has been carried out using X-ray diffraction (XRD), scanning electron microscopy, and magnetic measurements. The XRD results reveal that both compounds crystallized mainly in the Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> P-type hexagonal structure. The TS-prepared sample exhibits large holes and worse densification due to the evaporation of P, when comparing with the SPS-prepared sample. The Curie temperatures are found to be 251 and 291 K on cooling, and 261 and 298 K on heating for the compounds prepared by SPS and TS, respectively. For a field change of 3 T, the maximum values of isothermal entropy changes are found to be 15.1 and 7.9 J/kgK for the compounds prepared by SPS and TS, respectively. These results are correlated with the practical concentration of P in the compounds. This paper indicates that the SPS technique is suitable for synthesizing the Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> P-type bulks with good magnetocaloric properties.