Electromotive Force Induced by a Moving Magnetic Domain Wall

PAPER: S. A. Yang, G. S. D. Beach, C. Knutson, D. Xiao, Q. Niu, M. Tsoi, and J. L. Erskine, “Universal Electromotive Force Induced by DomainWall Motion”, Phys. Rev. Lett. 102, 067201 (2009)

ABSTRACT:

It is well known that an electric current traversing a magnetic domain wall can drive it into motion via coupling between conduction electrons and local magnetic moments. The inverse effect, in which an emf is induced by a moving magnetic domain wall, has also been predicted [1-3]. Recent calculations by Niu and co-workers [4] have shown that this emf should be universal in the sense that it is independent of the detailed domain-wall profile and depends only on the wall transformation frequency through a universal Josephson type relation, which is closely related to the topological nature of the domain wall. Here we describe the first experimental observation of an emf induced in a Permalloy nanowire by a field-driven domain wall [4]. Over a range of driving fields, we detect a small voltage generated during the motion of a single domain wall monitored by high-bandwidth scanning Kerr polarimetry. Our observations confirm the theoretical predictions, from which information about the wall motion can be extracted.

[1] L. Berger, Phys. Rev. B 33, 1572 (1986).

[2] S. E. Barnes et al., arXiv:cond-mat/0410021 (2004); Appl. Phys. Lett. 89, 122507 (2006).

[3] R. A. Duine, Phys. Rev. B 77, 014409 (2008).

[4] S. Yang et al., Phys. Rev. Lett. 102, 067201 (2009).

The authors thank C. Xu, W. Li, C.-P. Chuu, W. Yao, D. Clougherty, and S. Zhang for valuable discussions. S.Y., G. B., C. K., M. T., and J. E. were supported by NSF DMR-0404252, DX was supported by NSF DMR-0606485, G. B. and J. E. by theWelch Foundation, and Q. N. by DOE (DEFG03-02ER45958).