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The Effects of Small Metal Additions (Co, Cu, Ga, Mn, Al, Bi, Sn) on the Magnetocaloric Properties of the Gd5Ge2Si2 Alloy



Robert D. Shull, Virgil Provenzano, Alexander J. Shapiro, A Fu, M W. Lufaso, E Karapetrova, G Kletetschka, V Mikula


It was shown that adding one atomic percent Fe to Gd5Ge2Si2 greatly reduced its large hysteresis losses, broadened the magnetic entropy change, ?Sm, versus temperature, T, peak, and shifted the ?Sm peak value from 275 K to 305 K[1]. The present paper examines (1) the earlier conclusion that Fe doping prevents the formation of the Gd5Ge2Si2 monoclinic phase and (2) if there is anything unique about iron doping for causing the above beneficial changes. Accordingly, Gd5Ge2Si2 was doped with about one atom percent of other metal additives, including, Co, Cu, Ga, Mn, Al, Bi, and Sn. In addition low temperature x-ray diffraction measurements on the Fe-doped Gd5Ge2Si2 alloy were performed. It was observed that, in the 270 K to 330K temperature range, the addition of Cu, Ga, Mn, and Al completely eliminated the large hysteresis losses of the Gd5Ge2Si2 alloy and displayed the other magnetocaloric characteristics of the Fe-doped material; Co addition acted similarly. On the other hand, the addition of Bi or Sn had a negligible effect on the alloy hysteresis losses and on the characteristics of the Sm, vs. T peak. Similar to the earlier study with Fe-doping, the microstructures of the alloy doped with Co, Cu, Ga, Mn, or Al consisted of a majority phase and a minor intergranular phase. The majority phase was partially depleted of silicon, while the minority phase was rich in silicon and the corresponding metal additive, whereas for Bi or Sn addition, the microstructure consisted of only the Gd5Ge2Si2 phase. The low temperature x-ray results on the Fe-doped sample showed the same spectra at 245 K and 300 K, and that the spectra were consistent with the majority of the material possessing an orthorhombic structure. It is concluded that in addition to Fe other metal additives to Gd5Ge2Si2 also lead to greatly improved refrigerants.
Journal of Applied Physics


magnetocaloric properties, small metal additions


Shull, R. , Provenzano, V. , Shapiro, A. , Fu, A. , Lufaso, M. , Karapetrova, E. , Kletetschka, G. and Mikula, V. (2006), The Effects of Small Metal Additions (Co, Cu, Ga, Mn, Al, Bi, Sn) on the Magnetocaloric Properties of the Gd<sub>5</sub>Ge<sub>2</sub>Si<sub>2</sub> Alloy, Journal of Applied Physics, [online], (Accessed April 12, 2024)
Created April 26, 2006, Updated February 17, 2017