Calculation of the Amplitude of Acoustic Waves in Nanoscale Magnets in an Alternating Magnetic Field Caused by Displacements of Domain Boundaries

This paper proposes an algorithm that utilizes a macroscopic approach to calculate the amplitude of the total acoustic signal generated by an alternating magnetic field in ribbon-shaped nanocrystalline magnets (NCMs) with polydomain nanofibers at reversible displacements of domain boundaries. The calculations are made for the case with the wave vector directed along the magnetic field parallel to the tape plane. At the same time, the influence of anharmonicity on the displacements of the domain boundaries is considered for the carrier frequency. The orientation and frequency dependences for the wave vector and the signal absorption coefficient are found under the assumption that the rotation processes can be neglected. It is shown that the residual internal stresses in the (poly- or monodomain) nanograin NCMs have a significant effect on the absorption coefficient and the amplitude of the generated DG signal. The magnetic anisotropy constants decrease along with the size of the nanograins. In this case, the generation process due to the rotation of the spontaneous magnetization vectors is also significant, which must be considered in relation to the displacement processes. The proposed algorithm for calculating the amplitudes of the signals generated by a nanocrystalline magnet can be used to predict the friction properties of the developed promising NCM and calculate the amplitudes of the generated signals at the carrier frequency and harmonics.