Extraordinary Hall effect and universal scaling in Fex(ZnO)1–x granular thin films at room temperature

On the benefit of the concept of the so-called diluted magnetic oxides, Fex(ZnO)1–x (x = 0.50–0.85) granular thin films with different thickness through 2D and 3D percolation region were prepared by ion beam assisted deposition. All samples are ferromagnetic at room-temperature due to the ferromagnetic nature of the Fe-doped ZnO matrix, which is quite different from the superparamagnetic behavior in the insulator-matrix based granular films. Along with decreasing thickness, the Hall coefficient RS is largely enhanced. The maximum RS reaches 4.27 × 10−7 m3/C in ∼2.8 nm Fe0.6(ZnO)0.4 granular film, which is nearly 9 times larger than the RS (4.64 × 10−8 m3/C) of the ∼50 nm Fe0.6(ZnO)0.4 sample. Meanwhile, the RS could maintain in a wide temperature region from 10 K to 300 K and the Hall sensitivity reaches ∼130 V/AT at room-temperature. The scaling exponential of n = 1.7 ± 0.1 in σxy∼σxxn is observed, fitting well with the recent developed universal scaling theory characterized by n = 1.6 in the dirty limit.