Abstrakt
Materials with antiferromagnetic ordering are one of the most active research topics in current condensed matter physics. NaMnAs is a semiconducting antiferromagnet from group of I-II-V semiconductors. The Neél temperature is above room temperature, and the material exhibits uniaxial anisotropy. This makes NaMnAs an interesting material on the field of novel magnetic materials. Our poster presentation focuses on magneto-optical properties of bulk single-crystal samples of antiferromagnetic semiconductor NaMnAs. We present low temperature infrared magneto-transmission spectroscopy at low energies, where we observe magnon-like mode at ħω = 7 meV. With application of magnetic field along material's tetragonal axis, we observe splitting of the mode into 2 branches. The dispersion is linear with magnetic field and the extrapolated g-factor is approximately 2, which is in agreement with the expected value. The absence of interacting phonon modes in the vicinity of the magnon-like mode shows, that NaMnAs provides textbook example of antiferromagnetic resonance in easy-axis material. This statement is supported by magneto-transmission spectroscopy in additional geometry configurations.
The experimental results are accompanied with linear spin-wave theory simulation of dispersion of magnon in k-space. The simulation is based on the experiment discussed above and on ab initio theoretical predictions of exchange interactions. Theoretical predictions are developed from experimental measurements of optical properties of the material. To calculate the spin-wave simulation, we apply software package SpinW written for MATLAB. By correlating simulation results with experiment, we are able to determinate single-ion anisotropy energy.
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Physical Review B (Vol. 105, Issue 12). American Physical Society (APS).