Giant magnetoresistance in Ce2Fe17

Using a single-phase sample of Ce2Fe17 with the rhombohedral Th2Zn17-type structure, we measured the magnetization, resistivity, and specific heat under various magnetic fields up to 5.5 T. Below T-c = 125 K, giant magnetoresistance (GMR) is induced by the metamagnetic transition from the antiferromagnetic to ferromagnetic states. The value of Delta rho/rho(congruent to rho(AF)-rho(F))/rho(AF)) reaches 0.85 at 4.2 K, while the value gamma(congruent to C/T at 0 K) of 351 mJ/K-2/mole in zero field only decreases similar to 20% by the metamagnetic transition. These results suggest that GMR is due to the closing of a superzone ap formed by antiferromagnetic ordering of Fe spins, while the large gamma value is due to valence fluctuations of the Ce-4f electrons, weakly dependent on magnetic field.