Temperature and Magnetic Field Induced Phase Transformation in Bulk and Composite Gd_5Si_2Ge_2

摘要

A ―1300 ppm strain has been obtained in a, resin binder, Gd_5Si_2Ge_2 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 ≤ 600μm . Bulk Gd_5Si_2Ge_2 was manufactured via arc melting and subsequently annealed at 1300℃ 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 =-9.3℃, M_f =-14.6℃, A_s =-4.4?, and A_f =-1.2℃. 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.