Giant magnetocaloric effect enhanced by Pb-doping in Gd5Si2Ge2 compound

The influences of lead substitution on the phase formation, Curie temperature and magnetic entropy change of the monoclinic Gd5Ge2Si2 compound have been investigated. Five Pb-doped Gd5Si2−xGe2−xPb2x samples were prepared with 2x = 0, 0.01, 0.03, 0.05 and 0.10. Experimental results show that a small amount of Pb-doping in Gd5Ge2Si2 compound keeps the first-order structural/magnetic transition, significantly enhances its magnetocaloric effects as well as increase its Curie temperature Tc. The maximum magnetic entropy change in the magnetic field change of 0–2.0 T is 24.6 J kg−1 K−1 at 275 K for the sample Gd5Si1.995Ge1.995Pb0.01, and reaches 27.5 J kg−1 K−1 at 274 K for the sample Gd5Si1.975Ge1.975Pb0.05, which is nearly twice as lager as that of pure Gd5Si2Ge2 compound (14.1 J kg−1 K−1 at 260 K) in the same magnetic field change.