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Säubert, S.; Franz, C.; Jochum, J. K.; Benka, G.; Bauer, A.; Shapiro, S. M.; Böni, P.; Pfleiderer, C. Evolution of spin dynamics during freezing in the spin-glass FexCr1-x Journal Article Phys. Rev. B 110, 094422 (2024). Abstract | Links | BibTeX | Project(s): C1, C3 @article{saubert_evolution_2024,In the iron–chromium system, Fe𝑥Cr1−𝑥, a wide dome of spin-glass behavior emerges when the ferromagnetism of iron is suppressed and the antiferromagnetism of chromium emerges as a function of increasing iron content 𝑥. As both, the high-temperature state and the characteristic cluster size vary as a function of 𝑥, different regimes of spin-glass behavior may be compared in a single, isostructural material system. Here, we report a study of the spin dynamics across the freezing process into the spin-glass state for different iron concentrations (𝑥=0.145, 0.175, 0.21) using modulation of intensity with zero effort (MIEZE) spectroscopy. In the parameter range studied, the relaxation process observed experimentally may be described well in terms of a stretched exponential. In the reentrant cluster-glass regime, 𝑥=0.145, this behavior persists up to high temperatures. In comparison, in the superparamagnetic regime, 𝑥=0.175 and 𝑥=0.21, a single relaxation time at elevated temperatures is observed. For all samples studied, the spin relaxation exhibits a momentum dependence consistent with a power law, providing evidence of a dispersive character of the spin relaxation. |  |
Kalin, J.; Sievers, S.; Schumacher, H. W.; Füser, H.; Bieler, M.; Bauer, A.; Pfleiderer, C. Influence of the magnetovolume effect on the transient reflectivity of MnSi Journal Article Phys. Rev. B 110, 014415 (2024). Abstract | Links | BibTeX | Project(s): C1, C3 @article{kalin_influence_2024,The magnetovolume effect is a well established yet frequently overlooked phenomenon in magnetic materials that may affect a wide range of physical properties. Our study explores the influence of the magnetovolume effect on the transient reflectivity of MnSi, a well-known chiral magnet with strong magnetoelastic coupling. We observe a unipolar reflectivity transient in the paramagnetic phase, contrasting with a bipolar response in phases with magnetic long-range order. Comparing our findings with thermal expansion from literature, we establish that the bipolar response originates in the magnetovolume effect which dominates the thermal expansion and influences the optical reflectivity. Our results highlight not only that the magnetovolume effect must be considered when discussing transient reflectivity measurements of magnetic materials but also that such measurements permit to study the characteristic time scales of the magnetovolume effect itself, contributing to a deeper understanding of this often-neglected phenomenon. | |