Magnetocaloric Properties and Structure of the Gd 5 Ge 1.8 Si 1.8 Sn 0.4 Compund

In this study the magnetic properties and the structure of Gd₅Ge_1.8Si_1.8Sn_0.4 alloy were investigated by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and magnetometry. The concentration of the Sn-doping in this study is four times that used in previous studies examining the magnetocaloric properties of the Gd₅Ge₂Si₂ compound doped with different metal additives. In the earlier studies it was shown the addition of about one atom percent of either Fe, Cu, Co, Ga, Mn, or Al nearly eliminated the large hysteresis losses present in the undoped Gd₅Ge₂Si₂ compound between 270 K and 300 K. Also, these metal additives affected the characteristics DeltaS_m versus T peak, resulting in a significant increase in the refrigeration capacity of the material, if the hysteresis losses are taken into account. By contrast, the same amount of either Sn or Bi had much smaller effects on both the hysteresis losses and the characteristics of the DeltaS_m versus T peak. In this study, a larger amount of Sn doping had a limited effect on the hysteresis losses and characteristics of the DeltaS_m versus T peak of Gd₅Ge₂Si₂ . But, most importantly, it resulted in a different microstructure compared to the compound with smaller Sn addition. The implications of the larger Sn doping on both the magnetocaloric properties and structure of the Gd₅Ge₂Si₂ compound are discussed.