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Quadrupole anomalous Hall effect in magnetically induced electron nematic state
Hiroki Koizumi1,2,3, Yuichi Yamasaki4, Hideto Yanagihara5,6
1Department of Applied Physics, University of Tsukuba, Tsukuba, Ibaraki, 305-8573, Japan. hiroki.koizumi.d7@tohoku.ac.jp.
Nature Communications
|December 8, 2023
Summary
Researchers discovered an anisotropic linear anomalous Hall effect (AHE) in NiCo2O4 films, showing a unique quadrupole dependence controllable by magnetic-field cooling. This finding offers new insights into electron nematic states and off-diagonal transport phenomena.
Area of Science:
- Condensed matter physics
- Materials science
- Spintronics
Background:
- Berry phases induce transverse electron motion, leading to Hall effects like anomalous and topological Hall effects.
- These conventional Hall effects are typically isotropic in the plane perpendicular to the magnetic field.
Purpose of the Study:
- To investigate and report the manifestation of an anisotropic linear anomalous Hall effect (AHE) in NiCo2O4 epitaxial films.
- To explore the underlying mechanisms and controllability of this unconventional Hall effect.
Main Methods:
- Epitaxial thin film growth of NiCo2O4.
- Electrical transport measurements, including Hall effect measurements under varying current directions and magnetic field cooling protocols.
Main Results:
- Observation of an anisotropic linear AHE in NiCo2O4, deviating from the expected isotropic behavior.
- Identification of a quadrupole dependence on in-plane current direction superimposed on the uniform AHE.
- Demonstration that the sign of the anisotropic effect can be controlled via magnetic-field cooling.
Conclusions:
- The anisotropic AHE in NiCo2O4 is attributed to an electron nematic state.
- This nematic state arises from a deformed electronic structure associated with magnetic toroidal quadrupole and ferrimagnetic ordering.
- The findings provide a new platform for studying off-diagonal transport phenomena and electron nematicity.
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