Planar Hall Effect in MnSi

Abstract

In ferromagnets, the resistance measured with current parallel to magnetization and current perpendicular to magnetization is different, which is called anisotropic magnetoresistance (AMR) effect. In chiral magnets, spin modulation direction of a chiral spin structure is also expected to give rise to AMR effect. In this chapter, we have investigated planar Hall effect, which sensitively extracts anisotropic component of resistance. In the well-established skyrmion phase region of the bulk samples, a prominent stepwise field profile of planar Hall effect is observed, which results from AMR effect with respect to the spin modulation direction. We also detect the characteristic planar Hall anomalies in the thin plate samples fabricated with the use of a focused ion beam, which indicates the formation of skyrmion strings lying in the sample plane. Formation of metastable skyrmions in thin plate samples identified by using the measurement of planar Hall effect is also shown.