Giant magnetoresistance near the magnetostructural transition in Gd5(Si1.8Ge2.2)

Zero-field electrical resistivity over the temperature range of 4-300 K and magnetoresistance in magnetic fields of up to 12 T have been measured in Gd-5(Si1.8Ge2.2). This system undergoes a first-order magnetostructural transition at T-C congruent to 240 K, from a high-temperature paramagnetic to a low-temperature ferromagnetic phase, accompanied by a large drop in the resistivity. The application of an external magnetic field above T-C can induce this transition, and a giant negative magnetoresistance effect (Delta rho/rho congruent to -20%) is observed associated with this first-order field-induced transition. (C) 1998 American Institute of Physics. [S0003-6951(98)00449-5].