Universality of the helimagnetic transition in cubic chiral magnets: Small angle neutron scattering and neutron spin echo spectroscopy studies of FeCoSi

Abstract

Universality of the helimagnetic transition in cubic chiral magnets: Small angle neutron scattering and neutron spin echo spectroscopy studies of FeCoSi CopyrightOther than for strictly personal use, it is not permitted to download, forward or distribute the text or part of it, without the consent of the author(s) and/or copyright holder(s), unless the work is under an open content license such as Creative Commons. Takedown policyPlease contact us and provide details if you believe this document breaches copyrights. We will remove access to the work immediately and investigate your claim. We present a comprehensive small angle neutron scattering and neutron spin echo spectroscopy study of the structural and dynamical aspects of the helimagnetic transition in Fe 1−x Co x Si with x = 0.30. In contrast to the sharp transition observed in the archetype chiral magnet MnSi, the transition in Fe 1−x Co x Si is gradual, and long-range helimagnetic ordering coexists with short-range correlations over a wide temperature range. The dynamics are more complex than in MnSi and involve long relaxation times with a stretched exponential relaxation which persists even under magnetic field. These results in conjunction with an analysis of the hierarchy of the relevant length scales show that the helimagnetic transition in Fe 1−x Co x Si differs substantially from the transition in MnSi and question the validity of a universal approach to the helimagnetic transition in chiral magnets.

Nanosecond X-Ray Photon Correlation Spectroscopy on Magnetic Skyrmions

“…Our data are consistent with other Skyrmion work such as GHz ferromagnetic resonance (FMR) modes observed in a similar Fe/Gd system [50], as well as with recent neutron spin echo spectroscopy experiments on fluctuating magnetic correlations in FeCoSi [51].…”

Magnetic Fluctuations, Precursor Phenomena, and Phase Transition in MnSi under a Magnetic Field

“…This approach provides a good description of the temperature dependence of the correlation length and the susceptibility in MnSi [12]. However, it does not satisfactorily describe all observations [16] and is less conclusive for other chiral magnets such as Cu 2 OSeO 3 [21] and Fe 0.7 Co 0.3 Si [23]. Thus the origin of the first order phase transition in helimagnets and its connection to the fluctuating correlations and precursor phenomena above T C is still an open question that is addressed in this Letter for the case of MnSi.…”

Pinning Effects of Exchange and Magnetocrystalline Anisotropies on Skyrmion Lattice

“…Then, by plotting the deformation-related parameters as functions of one exchange anisotropy, we figure out that the deformation of SkX is characterized by the change of amplitudes, lengths and azimuth angles of wave vectors. Next, we compare our results with some experiments, the fourth order magnetocrystalline anisotropy may explain the pinning of SkX in MnSi [1,25,26] and Fe 1−x Co x Si [12,[27][28][29]. To reproduce the 30 + rotation of SkX in Cu 2 OSeO 3 [16], we consider both the exchange and magnetocrystalline anisotropy, and find that at certain conditions 30 + rotation of SkX occurs when temperature or magnetic field changes.…”