2024
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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). @article{saubert_evolution_2024,
title = {Evolution of spin dynamics during freezing in the spin-glass Fe_{x}Cr_{1-x}},
author = {S. Säubert and C. Franz and J. K. Jochum and G. Benka and A. Bauer and S. M. Shapiro and P. Böni and C. Pfleiderer},
doi = {10.1103/PhysRevB.110.094422},
year = {2024},
date = {2024-09-13},
urldate = {2024-09-13},
journal = {Phys. Rev. B},
volume = {110},
number = {9},
pages = {094422},
abstract = {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.},
keywords = {C1, C3},
pubstate = {published},
tppubtype = {article}
}
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). @article{kalin_influence_2024,
title = {Influence of the magnetovolume effect on the transient reflectivity of MnSi},
author = {J. Kalin and S. Sievers and H. W. Schumacher and H. Füser and M. Bieler and A. Bauer and C. Pfleiderer},
doi = {10.1103/PhysRevB.110.014415},
year = {2024},
date = {2024-07-11},
urldate = {2024-07-11},
journal = {Phys. Rev. B},
volume = {110},
number = {1},
pages = {014415},
abstract = {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.},
keywords = {C1, C3},
pubstate = {published},
tppubtype = {article}
}
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. | |
Müller, M.; Weber, J.; Engelhardt, F.; Bittencourt, V. A. S. V.; Luschmann, T.; Cherkasskii, M.; Opel, M.; Goennenwein, S. T. B.; Kusminskiy, S. V.; Geprägs, S.; Gross, R.; Althammer, M.; Huebl, H. Chiral phonons and phononic birefringence in ferromagnetic metal–bulk acoustic resonator hybrids Journal Article Phys. Rev. B 109, 024430 (2024). @article{muller_chiral_2024,
title = {Chiral phonons and phononic birefringence in ferromagnetic metal–bulk acoustic resonator hybrids},
author = {M. Müller and J. Weber and F. Engelhardt and V. A. S. V. Bittencourt and T. Luschmann and M. Cherkasskii and M. Opel and S. T. B. Goennenwein and S. V. Kusminskiy and S. Geprägs and R. Gross and M. Althammer and H. Huebl},
doi = {10.1103/PhysRevB.109.024430},
year = {2024},
date = {2024-01-23},
urldate = {2024-01-01},
journal = {Phys. Rev. B},
volume = {109},
number = {2},
pages = {024430},
abstract = {Magnomechanical devices, in which magnetic excitations couple to mechanical vibrations, have been discussed as efficient and broadband microwave signal transducers in the classical and quantum limit. We experimentally investigate the resonant magnetoelastic coupling between the ferromagnetic resonance modes in metallic Co25Fe75 thin films, featuring ultralow magnetic damping as well as sizable magnetostriction, and standing transverse elastic phonon modes in sapphire, silicon, and gadolinium gallium garnet at cryogenic temperatures. For all substrates, we observe a coherent interaction between the acoustic and magnetic modes. We identify the phonon modes as transverse shear waves propagating with slightly different velocities (Δv/v≃10−5); i.e., all investigated substrates show potential for phononic birefringence as well as phonon-mediated angular momentum transport. Our magnon-phonon hybrid systems operate in a coupling regime analogous to the Purcell enhanced damping in cavity magnonics.},
keywords = {C3},
pubstate = {published},
tppubtype = {article}
}
Magnomechanical devices, in which magnetic excitations couple to mechanical vibrations, have been discussed as efficient and broadband microwave signal transducers in the classical and quantum limit. We experimentally investigate the resonant magnetoelastic coupling between the ferromagnetic resonance modes in metallic Co25Fe75 thin films, featuring ultralow magnetic damping as well as sizable magnetostriction, and standing transverse elastic phonon modes in sapphire, silicon, and gadolinium gallium garnet at cryogenic temperatures. For all substrates, we observe a coherent interaction between the acoustic and magnetic modes. We identify the phonon modes as transverse shear waves propagating with slightly different velocities (Δv/v≃10−5); i.e., all investigated substrates show potential for phononic birefringence as well as phonon-mediated angular momentum transport. Our magnon-phonon hybrid systems operate in a coupling regime analogous to the Purcell enhanced damping in cavity magnonics. |  |
2023
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Müller, M.; Weber, J.; Goennenwein, S. T. B.; Kusminskiy, S. V.; Gross, R.; Althammer, M.; Huebl, H. Temperature dependence of the magnon-phonon interaction in high overtone bulk acoustic resonator-ferromagnetic thin film hybrids Journal Article Phy. Rev. Applied 21, 034032 (2023). @article{muller_temperature_2023,
title = {Temperature dependence of the magnon-phonon interaction in high overtone bulk acoustic resonator-ferromagnetic thin film hybrids},
author = {M. Müller and J. Weber and S. T. B. Goennenwein and S. V. Kusminskiy and R. Gross and M. Althammer and H. Huebl},
doi = {10.1103/PhysRevApplied.21.034032},
year = {2023},
date = {2023-01-01},
urldate = {2023-01-01},
journal = {Phy. Rev. Applied},
volume = {21},
number = {3},
pages = {034032},
keywords = {C3},
pubstate = {published},
tppubtype = {article}
}
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