SKM 2023 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 46: Ultrafast Magnetization Effects II

MA 46.1: Vortrag

Freitag, 31. März 2023, 09:30–09:45, HSZ 02

Spin noise in magnetically ordered models — •Julius Schlegel, Martin Evers, and Ulrich Nowak — Department of Physics, University of Konstanz

Spin noise spectroscopy has emerged in the last years as a new tool to investigate magnetic material properties [1].

On the basis of a classical Heisenberg model and the stochastic Landau-Lifshitz-Gilbert equation of motion we numerically compute the time evolution of magnetically ordered structures on a time scale of several hundreds of picoseconds. By analyzing the spectral noise power density and the autocovariance of the magnetization in both ferro- and antiferromagnetic models, we find that the magnetic noise in thermal equilibrium comprises several features of the system. Resonances in the noise spectra are observed, which can be assigned to the eigenmodes of the magnetic structure. Moreover, the noise can mark phase transitions like the transition to the paramagnetic state or a spin-flop transition.

We thus conclude that by means of investigating the noise of the magnetization, the magnetic order of a system can be extracted even in cases where the mean equilibrium magnetization does not reflect the transition at all.

[1] Valerii S. Zapasskii, "Spin-noise spectroscopy: from proof of principle to applications", Adv. Opt. Photon. 5, 131-168 (2013)