Abstract
The results of studying the possibility of measuring the energy gap of a nonfield nature in the spectrum of spin waves in ferromagnets are presented. As a research method, the technique of the small-angle scattering of polarized neutrons in inclined geometry is used, which allows one to separate the contribution of inelastic scattering. Inelastic scattering can be obtained as the difference between the intensities when the neutron beam is polarized along and against the direction of the magnetic field. Spin-wave scattering is concentrated in a cone limited by the cutoff angle θC. It is shown that the square of the cutoff angle linearly depends on the magnetic field H and the energy gap Δ of nonfield nature: \(\theta _{{\text{C}}}^{2}\left( H \right) = \theta _{0}^{2} - \left( {g\mu H + \Delta } \right){{{{\theta }_{0}}} \mathord{\left/ {\vphantom {{{{\theta }_{0}}} E}} \right. \kern-0em} E}\). The parameter \({{\theta }_{0}} = {{\hbar }^{2}}\frac{1}{{2D{{m}_{n}}}}\) is inversely proportional to the constant spin-wave stiffness D of the material. Model calculations for the experiment on small-angle neutron scattering are presented. They convincingly show the possibility of measuring not only the spin-wave stiffness with an accuracy of several percent, but also the nonfield gap Δ with an accuracy of up to 1 μeV. The calculation technique is applied to the results of studying the classical Fe65Ni35 invar alloy at room temperature.
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ACKNOWLEDGMENTS
We are grateful to Helmut Eckerlebe for help in carrying out the experiment on the small-angle scattering of polarized neutrons.
Funding
This work was supported by the Ministry of Science and Higher Education of the Russian Federation within the framework of agreement no. 075-15-2022-830 of May 27, 2022 (prolongation of agreement no. 075-15-2021-1358 of October 12, 2021).
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Translated by A. Nikol’skii
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Azarova, L.A., Vinogradov, R.M., Pshenichniy, K.A. et al. On the Possibility of Measuring the Energy Gap in the Spectrum of Spin Waves of Ferromagnets by the Small-Angle Scattering of Polarized Neutrons. J. Surf. Investig. 16, 1253–1262 (2022). https://doi.org/10.1134/S1027451022060313
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DOI: https://doi.org/10.1134/S1027451022060313