Magnetocaloric effect in high-energy ball-milled Gd5Si2Ge2 and Gd5Si2Ge2/Fe nanopowders

Evolution of structure and magnetocaloric properties in ball-milled Gd5Si2Ge2 and Gd5Si2Ge2/0.1wt% Fe nanostructured powders were investigated. The high-energy ball-milled powders were composed of very. ne grains (70-80 nm). Magnetization decreased with milling time due to decrease in the grain size and randomization of the magnetic moments at the surface. The magnetic entropy change (Delta S-M) was calculated from the isothermal magnetization curves and a maximum value of 0.45 J/kgK was obtained for 32h milled Gd5Si2Ge2 alloy powder for a magnetic field change of 2T while it was still low in Fe-contained alloy powders. The thermo-magnetic measurements revealed that the milled powders display distribution of magnetic transitions, which is desirable for practical magnetic refrigerant to cover a wide temperature span. (c) 2008 Elsevier B.V. All rights reserved.