Anomalous Hall Effect and Perpendicular Magnetic Anisotropy in Ultrathin NiCo<sub>2</sub>O<sub>4</sub> Films

ORAL

Abstract

The high Curie temperature (TC) and high spin polarization of ferrimagnetic spinel NiCo2O4 (NCO) make it a promising material candidate for spintronic applications.1 We report the magnetotransport study of 1.5 uc (unit cell) to 5 uc (1.2-4 nm) epitaxial NCO thin films deposited on (001) MgAl2O4 substrates. The 3 uc and thicker NCO films exhibit metallic conduction, while the 1.5 and 2 uc films become totally insulating. Samples of all thicknesses exhibit anomalous Hall effect (AHE) below TC, with the AHE switching hysteresis revealing strong perpendicular magnetic anisotropy. For all films, the coercive field HC increases exponentially with decreasing temperature, which can be attributed to thermally activated domain wall depinning. The AHE resistance shows a nonmonotonic temperature dependence and reverses sign at low temperature. The scaling between the AHE conductivity σxy and longitudinal conductivity σxx points to the dominating dirty metal behavior. We also discuss the topological Hall effect and magnetic force microscopy studies of the ultrathin NCO films.

*This work was supported by NSF through DMR-1710461 and OIA-2044049.

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Publication: 1. Chen et al., Adv. Mater. 31, 1805260 (2019).

Presenters

  • Qiuchen Wu

    • University of Nebraska - Lincoln

Authors

  • Qiuchen Wu

    • University of Nebraska - Lincoln

  • Xuegang Chen

    • Anhui University

  • Xia Hong

    • Department of Physics and Astronomy & Nebraska Center for Materials and Nanoscience, University of Nebraska-Lincoln
    • Department of Physics and Astronomy & Nebraska Center for Materials and Nanoscience, University of Nebraska - Lincoln
    • University of Nebraska-Lincoln
    • University of Nebraska, Lincoln