Temperature and magnetic field induced phase transformation in bulk and composite Gd5Si2Ge2

A - 1300ppm strain has been obtained in a [0-3], resin binder, Gd5Si2Ge2 particulate composite. The strain is a result of a temperature 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 less than or equal to600 mum. Bulk Gd5Si2Ge2 was manufactured via arc melting and subsequently annealed at 1300degreesC 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 M-s =-93degreesC, M-f = -14.6degreesC, A(s) = -4.4degreesC, and A(f) = -1.2degreesC. The bulk sample was 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 - 8000ppm volume magnetostriction, agreeing well with measured unit cell parameters of the different phases.