Unidirectional planar Hall voltages induced by surface acoustic waves in ferromagnetic thin films

Takuya Kawada, Masashi Kawaguchi, and Masamitsu Hayashi
Phys. Rev. B 99, 184435 – Published 24 May 2019

Abstract

The electromotive forces induced by surface acoustic waves (SAWs) are investigated in ferromagnetic thin films. CoFeB thin films deposited on LiNbO3 substrates are patterned into Hall bars to study the acoustoelectric transport properties of the device. The longitudinal and transverse dc voltages that develop in the Hall bars, which are parallel and orthogonal to the flow of the SAW, respectively, are measured under application of an in-plane magnetic field. The longitudinal voltage scales linearly with the SAW power and reverses its polarity upon changing the direction to which the SAW propagates, suggesting generation of a dc acoustic current via the SAW excitation. The magnetic field has little influence on the acoustic current. In contrast, the SAW induced transverse voltage shows significant dependence on the relative angle between the magnetic field and the SAW propagation direction. Such field angle dependent voltage resembles that of the planar Hall voltage induced by electric current. Interestingly, the angle dependent acoustic transverse voltage does not depend on the SAW propagation direction. Moreover, the magnitude of the equivalent angle dependent acoustic transverse resistance is more than one order of magnitude larger than that of the planar Hall resistance. These results show the unique acoustoelectric transport properties of ferromagnetic thin films.

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  • Received 20 February 2019
  • Revised 27 March 2019

DOI:https://doi.org/10.1103/PhysRevB.99.184435

©2019 American Physical Society

Physics Subject Headings (PhySH)

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

Takuya Kawada1, Masashi Kawaguchi1, and Masamitsu Hayashi1,2

  • 1Department of Physics, The University of Tokyo, Tokyo 113-0033, Japan
  • 2National Institute for Materials Science, Tsukuba 305-0047, Japan

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Issue

Vol. 99, Iss. 18 — 1 May 2019

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