Forced Volume Magnetostriction in Composite Gd5Si2Ge2

A -1200 ppm forced volume magnetostriction has been obtained in a [0-3], resin binder, Gd5Si2Ge2 particulate composite. The strain is a result of a magnetically induced phase transformation from a high volume (high temperature, low magnetic field) monoclinic phase to a low volume (low temperature, high magnetic field) orthorhombic phase. The particles used in the composite were ball-milled from a bulk sample and were sieved to obtain a size distribution of ∼> 600 (micro)m. Bulk Gd5Si2Ge2 was manufactured via arc melting and subsequently annealed at 1300 C for 1 hour to produce a textured, polycrystalline sample. The transformation temperatures of the bulk sample, as measured using a Differential Scanning Calorimeter (DSC), were Ms= -9.3 C, Mf=-14.6 C, As=-4.4 C, and Af=-1.2 C. The composite and the bulk samples were magnetically characterized using a SQUID magnetometer, and found to undergo a paramagnetic to ferromagnetic transition during the phase transformation, consistent with published results. The bulk sample was also found to possess a maximum linear magnetostriction -2500 ppm