Tunneling anomalous Hall effect in the nanogranular CoFe-B-Al-O films near the metal-insulator transition

Abstract

We present results of experimental studies of structural, magneto-transport and magnetic properties of CoFe-B-Al-O films deposited onto a glass ceramic substrate by the ion-beam sputtering of the target composed of Co40Fe40B20 and Al2O3 plates. The system consists on the strained crystalline CoFe metallic nanogranules with the size 2-5 nm which are embedded into the B-Al-O oxide insulating matrix. Our investigations are focused on the anomalous Hall effect (AHE) resistivity Rh and longitudinal resistivity R at T=5-200 K on the metallic side of metal-insulator transition in samples with the metal content x=49-56 at.%, that nominally corresponds to (Co40Fe40B20)x(Al2O3)100-x in the formula approximation. The conductivity at T > 15 K follows the lnT behavior that matches a strong tunnel coupling between nanogranules. It is shown that the scaling power-laws between AHE resistivity and longitudinal resistivity strongly differ, if temperature T or metal content x are variable parameters: Rh(T)~R(T)^0.4-0.5 obtained from the temperature variation of R and Rh at fixed x, while Rh(x)/x~R(x)^0.24, obtained from measurements at the fixed low temperature region (10-40 K) for samples with different x. We qualitatively describe our experimental data in the frame of phenomenological model of two sources of AHE e.m.f. arising from metallic nanogranules and insulating tunneling regions, respectively, at that the tunneling AHE (TAHE) source is strongly shunted due to generation of local circular Hall currents. We consider our experimental results as the first experimental proof of the TAHE manifestation.

27 pages, 12 figures

References in corpus (14)

• Anomalous Hall effect
• Training and Operation of an Integrated Neuromorphic Network Based on Metal-Oxide Memristors
• Granular Electronic Systems
• Proper Scaling of the Anomalous Hall Effect
• Intrinsic vs. extrinsic anomalous Hall effect in ferromagnets
• Quantum transport theory of anomalous electric, thermoelectric, and thermal Hall effects in ferromagnets
• Multivariable Scaling for the Anomalous Hall Effect
• Coulomb effects in granular materials at not very low temperatures
• The Scaling of the Anomalous Hall Effect in the Insulating Regime
• Anomalous Hall effect in granular ferromagnetic metals and effects of weak localization
• Quantum Size Effect transition in percolating nanocomposite films
• Giant Forward Scattering Asymmetry and Anomalous Tunnel Hall effect at Spin-Orbit-and Exchange-Split Interfaces
• Absence of the Ordinary and Extraordinary Hall effects scaling in granular ferromagnets at metal-insulator transition
• Resistance minimum and electrical conduction mechanism in polycrystalline CoFeB thin films

Cited by in corpus (7)

• Multifilamentary character of anticorrelated capacitive and resistive switching in memristive structures based on (CoFeB)x(LiNbO3)100-x nanocomposite
• Skew Andreev reflection in ferromagnet/superconductor junctions
• Anomalous Josephson Hall effect charge and transverse spin currents in superconductor/ferromagnetic insulator/superconductor junctions
• Unconventional Josephson supercurrent diode effect induced by chiral spin-orbit coupling
• Theory of the Anomalous Tunnel Hall Effect at Ferromagnet-Semiconductor Junctions
• Transport Signatures of Radial Rashba Spin-Orbit Coupling at Ferromagnet/Superconductor Interfaces
• Specific features of g $\approx$ 4.3 EPR line behavior in magnetic nanogranular composites