Dresden 2009 – scientific programme

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MA: Fachverband Magnetismus

MA 13: Poster Ia: Electron Theory (1); Magnetic Imaging (2,3); Thin Films (4-25); MSMA (26-33); Magn. Semiconductors (34-42); Magn. Half Metals and Oxides (43-60)

MA 13.48: Poster

Tuesday, March 24, 2009, 10:15–13:00, P1A

Universal scaling relation between Hall and longitudinal conductivity in Zn-substituted magnetite — Deepak Venkateshvaran, Andrea Nielsen, Matthias Althammer, Sebastian Goennenwein, •Matthias Opel, and Rudolf Gross — Walther-Meißner-Institut, Bayerische Akademie der Wissenschaften, Garching, Germany

The anomalous Hall effect (AHE) in the low-conductivity ferromagnetic oxide Fe_3−xZn_xO₄ with x = 0, 0.1, and 0.5 is investigated in this work. We used (001), (110), and (111) oriented epitaxial Fe_3−xZn_xO₄ films deposited on MgO and sapphire substrates in different oxygen partial pressures to analyze the dependence of the AHE on crystallographic orientation, Zn content, strain state, and oxygen deficiency. Despite substantial differences in their magnetic and transport properties, a universal scaling relation between the anomalous Hall conductivity σ_xy^AHE and the longitudinal conductivity σ_xx is observed. Specifically, we find that σ_xy^AHE ∝ σ_xx^α where α = 1.69±0.08. Our results agree with a recent theoretical prediction for metallic ferromagnets in the dirty limit [2], extending the theory to materials for which hopping conduction prevails. The fact that the scaling relation is independent of crystallographic orientation, Zn content, strain state, and oxygen deficiency suggests that it is universal and does not depend on the detailed nature of the transport mechanism. This work is supported by the DFG within SPP 1157 and 1285 and by the DAAD.

References: [1] D. Venkateshvaran et al., Phys. Rev. B 78, 092405 (2008). [2] S. Onoda et al., Phys. Rev. Lett. 97, 126602 (2006).