Giant Hall effect in granular Fe–SiO2 film

Abstract

We have studied the resistivity, magnetoresistivity, and Hall resistivity for a few Fex(SiO2)1−x granular films with Fe volume fraction x near the metal insulator transition threshold xc. Both the ordinary Hall coefficient R0 and the saturated extraordinary Hall resistivity ρxys were found to be enhanced by a factor of 104 when x approaches xc. The largest measurable R0 and ρxys at room temperature are about 10−3 μΩ cm/G and 250 μΩ cm, respectively. By comparing with the Ni-rich NiFe–SiO2 system [A. B. Pakhomov, X. Yan, and B. Zhao, Appl. Phys. Lett. 67, 3497 (1995)], we found that the correlation between giant Hall effect and the resistivity with a −log T-like dependence is independent of the sign of the carrier. The feasibility of using such a system as a magnetic-field sensor is discussed.

Scaling of the anomalous Hall current in Fe100−x(SiO2)Xu1, Zhang2, Wang3 et al. 2011Phys. Rev. B

“…This may also explain why the percolation threshold is about 30% SiO 2 , being lower than 50% as previously reported. 12 However, the existence of iron oxide in the films does not affect the interpretation of the observation here because the iron oxide played the same role as the insulating SiO 2 .…”

“…No mechanism was suggested to be responsible for giant AHE in this system. Yan and Zhao 12 studied the Hall effect in the Fe x (SiO 2 ) 100−x granular films of 0.5 μm thickness with x = 67, 56, 53, 52, and 50, i.e., the metal volume fraction above the percolation threshold. They found that both the ordinary Hall resistivity and the AHE resistivity increased about four orders in magnitude as x decreased from 100 to 50.…”

“…As Br substitution increases, the electrical conduction (longitudinal resistivity) in CuCr 2 Se 4−x Br x might be described by the three-dimensional (3D) bond percolation model. 18 It is well known that the metal-insulator granular materials also show the percolation behavior as the metal volume fraction decreases 11,12,[18][19][20] and may be described by the bond percolation model. 20 Therefore, it is interesting to explore if there is the same correlation ρ In this study, Fe 100−x (SiO 2 ) x granular films were chosen because Fe is a simple ferromagnet and AHE in pure iron crystal has been demonstrated to be intrinsic by the numerical calculations.…”

“…The anomalous Hall effect in magnetic granular films was studied by different groups [11][12][13] in the 1990s. Pakhomov et al observed the giant anomalous Hall effect in Ni x (SiO 2 ) 100−x , where AHE increased nearly four orders in magnitude as x decreased from 100 to 53 or in the vicinity of the percolation threshold.…”

Anomalous Hall effect in Fe/Au multilayers

“…This means that the AHE is directly related to the density and strength of the scattering from the interfaces and grain boundaries. In inhomogeneous systems, like granular thin films, both the composition and the particle size of the nonmagnetic material doped in the samples affect the AHE, which explains why various scaling relations have been reported for very similar granular thin films, e.g., Fe-SiO 2 films, by different groups [5,25,26]. In the present work, the influence of composition variation was avoided in the scaling relation and only the amount of interfacial scattering differs between the different samples.…”