Giant magnetoresistance near the magnetostructural transition in Gd-5(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 G d-5(Si1.8Ge2.2). This system undergoes a first-order magnetostructural tran sition 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 re sistivity. The application of an external magnetic field above T-C can indu ce this transition, and a giant negative magnetoresistance effect (Delta rh o/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].