Abstract
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. Twofold magnetic Bragg spots appearing below the magnetic transition temperature indicate the formation of a spin helix with a single propagation vector aligned perpendicular to the film plane. Due to magnetic anisotropy, the direction of is unaffected by an external magnetic field . Instead we observe anisotropic deformations of the spin helix with respect to the direction. In the configuration with , the helical pitch exhibits hysteretic elongation with , while the system tends to maintain an integer number of spiral turns within the film thickness by continuously pushing out one turn. For , the helix is smoothly distorted to a conical structure with minimal change in the magnetic period. The direct measurement of by SANS establishes a correspondence between helix deformation and macroscopic features observed in magnetization and magnetoresistivity.
- Received 31 August 2016
DOI:https://doi.org/10.1103/PhysRevB.94.184432
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