The 'magnetic ripple' state in weak ferromagnetic FeBO3:Mg

The transition from a homogeneous into a modulated magnetic state in weak ferromagnet FeBO3:Mg is studied by a magneto optic method. At T≤135 K, the application of a magnetic field in the weak plane of the crystal is shown to excite the modulation of its magnetic order parameter, which manifests itself in a periodic deviation of the local ferromagnetism vector from the magnetization direction. The modulation period and the azimuthal angle specifying the local ferromagnetism vector direction in the modulated magnetic state of the crystal are studied as a function of temperature and magnetic field. The results obtained are discussed in terms of the 'magnetic ripple' theory. (authors)