Regensburg 2025 – scientific programme
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MA: Fachverband Magnetismus
MA 33: Non-Skyrmonic Magnetic Textures I
MA 33.11: Talk
Thursday, March 20, 2025, 12:15–12:30, H16
Magnetic Ordering Temperature for Spin Spiral materials — •Varun Rajeev Pavizhakumari and Thomas Olsen — CAMD, Department of Physics, Technical University of Denmark, 2800 Kgs. Lyngby Denmark
Spin Spirals are the materials that show a helical arrangement of magnetic moments in the ground state. Thermal fluctuations from this state form collective excitations known as spin waves/magnons. As the thermal stability of a spin spiral is a decisive factor for its technological applications, there is considerable interest in the theoretical prediction of its critical temperature. This could be accomplished using two approaches - Holstein-Primakoff(HP) bosonization and the Green’s function-Random Phase Approximation(RPA) where we can calculate the thermally renormalized magnon energies at each temperature. But these methods only exist for ferromagnetic and a few specific antiferromagnetic materials. In this work, we propose a single-Q spiral generalization of the HP bosonization and the Green’s function-RPA to calculate the critical temperature. We benchmark these methods along with the classical Monte Carlo simulations and the Mean field theory, using their experimental exchange parameters for a diverse range of materials ; MnO and NiO(single site Neel state),MnF2(altermagnetic),Cr2O3 and Fe2O3(two site Neel state) and Ba3NbFe3Si2O14(incommensurate). In all cases, we observe that the Green’s function-RPA shows excellent agreement to the experiments and hence is as an ideal candidate to predict the critical temperature for any single-Q spirals.
Keywords: Magnons in Spin Spirals; Critical temperature; Heisenberg model; Holstein-Primakoff bosonization; Random Phase Approximation