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 Tc=125 K, giant magnetoresistance (GMR) is induced by the metamagnetic transition from the antiferromagnetic to ferromagnetic states. The value of Δρ/ρ(≅ρAF-ρF)/ρ AF) reaches 0.85 at 4.2 K, while the value γ(≅C/T at 0 K) of 351 mJ/K2/mole in zero field only decreases ∼20% by the metamagnetic transition. These results suggest that GMR is due to the closing of a superzone gap formed by antiferromagnetic ordering of Fe spins, while the large γ value is due to valence fluctuations of the Ce-4f electrons, weakly dependent on magnetic field.