Magnetization fluctuations and magnetic after-effect probed via the anomalous Hall effect
Year: 2024
Type: article
Abstract: Taking advantage of the anomalous Hall effect, we electrically probe low-frequency magnetization fluctuations at room temperature in a thin ferromagnetic Pt / Co / AlO x layer stack with perpendicular magnetic anisotropy. We observe a strong enhancement of the Hall voltage fluctuations within the hysteretic region of the magnetization loop. Analyzing both the temporal evolution of the anomalous Hall voltage and its frequency-dependent noise power density, we identify two types of magnetic noise: abrupt changes in the magnetic domain configuration, evident as Barkhausen-like steps in the Hall voltage time trace, yield a noise power density spectrum scaling with frequency as 1 / f β with β ≈ 2.0 . In contrast, quasistationary magnetization configurations are connected with a magnetic noise power density with an exponent β ≈ 1.0 . The observation of Barkhausen steps and relaxation effects shows that the magnetic system is in a nonstationary state in the hysteresis region, such that the fluctuation-dissipation theorem cannot be expected to hold. However, the time-dependent change in the Hall voltage for constant magnetic field strength resembles the integrated noise power. Published by the American Physical Society 2024
Source: Physical Review Research
Institutions: University of Konstanz, ETH Zurich, University of Göttingen
Language: English
Subfield: Atomic and Molecular Physics, and Optics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $2,625
Funder: Deutsche Forschungsgemeinschaft
OpenAlex ID: W4405424059