Anisotropic Chemical Pressure Effect on the Antiferromagnetic Kondo Semiconductor Ce(Ru1-xFex)2Al10

We have studied the Fe substitution effect on the anomalous antiferromagnetic (AFM) order in CeRu2Al10 by using both single- and poly-crystalline samples. Electron probe microanalysis revealed that the single crystals of Ce(Ru1-xFex)2Al10 with 0.5 ≤ x ≤ 0.8, grown by an Al self flux method, separate into Ru-rich central part and Fe-rich surface part. On the other hand, the composition in the polycrystalline samples is homogeneous. The magnetic susceptibility, electrical resistivity and specific heat measurements on the polycrystals indicate that TN gradually decreases and disappears at x = 0.7. This is contrasting to the pressure induced peaking of TN at 2.5 GPa. We should remind that application of hydrostatic pressure and Fe substitution result in different lattice contractions. The rate of contraction by the hydrostatic pressure is almost isotropic up to Pc = 4 GPa, while that by Fe substitution is strongly anisotropic; Δa/a ≈ Δc/c ≈ 2Δb/b. Therefore, the contrasting changes of TN by Fe substitution and by hydrostatic pressure suggest that the degree of c-f hybridization along the b-axis controls the anomalous AFM order in CeRu2Al10.