Modulated magnetic structure of a nonuniformly stressed FeBO3 single crystal

The magnetization of a nonuniformly stressed FeBO₃ crystal along any of the two specific directions in the basal plane (the easy plane) at a temperature of T < 140 K in a magnetic field exceeding the threshold value H ₀ is found to lead to a transition of the crystal from the uniform magnetic state to the spatially modulated one. The modulated magnetic phase arising under these conditions exists in a certain temperature-dependent field range H ₀ ≤ H ≤ H _c and is representable in the form of a static spin wave that is linearly polarized in the easy plane of the crystal and has a wave vector k oriented at an angle of ～30° to the magnetization axis. The field, temperature, and orientation dependences of k are investigated. A physical mechanism is proposed to explain the modulation of the magnetic order parameter of the crystal under study. The results obtained are discussed in terms of the magnetic ripple theory.