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Direct observation of anisotropic magnetic field response of the spin helix in FeGe thin films

Type of publication Peer-reviewed
Publikationsform Original article (peer-reviewed)
Author Kanazawa N., White J. S., Rønnow H. M., Dewhurst C. D., Fujishiro Y., Tsukazaki A., Kozuka Y., Kawasaki M., Ichikawa M., Kagawa F., Tokura Y.,
Project Exploration of emerging magnetoelectric coupling effects in new materials
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Original article (peer-reviewed)

Journal Physical Review B
Volume (Issue) 94(18)
Page(s) 184432 - 184432
Title of proceedings Physical Review B
DOI 10.1103/physrevb.94.184432


We report the observation by small-angle neutron scattering (SANS) of a magnetic helical structure confined in a thin film of the chiral lattice magnet FeGe. Twofoldmagnetic Bragg spots appearing belowthemagnetic transition temperature indicate the formation of a spin helix with a single propagation vector q aligned perpendicular to the film plane. Due to magnetic anisotropy, the direction of q is unaffected by an external magnetic field H. Instead we observe anisotropic deformations of the spin helix with respect to the H direction. In the configuration with H ⊥ q, the helical pitch exhibits hysteretic elongation with H, while the system tends to maintain an integer number of spiral turns within the film thickness by continuously pushing out one turn. For H q, the helix is smoothly distorted to a conical structure with minimal change in the magnetic period. The direct measurement of q by SANS establishes a correspondence between helix deformation and macroscopic features observed in magnetization and magnetoresistivity.