Controlling the Dzyaloshinskii-Moriya interaction to alter the chiral link between structure and magnetism forFe1−xCoxSi

Abstract

Monosilicides of 3d-metals frequently show a chiral magnetic ordering with the absolute configuration defined by the chirality of the crystal structure and the sign of the Dzyaloshinskii-Moriya interaction (DMI). Structural and magnetic chiralities are probed here for Fe1−xCoxSi series and their mutual relationship is found to be dependent on the chemical composition. The chirality of crystal structure was previously shown to be governed by crystal growth, and the value of the DMI is nearly the same for all monosilicides of Fe, Co and Mn. Our findings indicate that the sign of the DMI in Fe1−xCoxSi is controlled by the Co composition x. We have been able to directly measure the change of the link between structure and magnetism in this helimagnetic B20 alloy.PACS numbers: 61.12.Ex, Scattering of polarized neutrons on chiral magnetic structures allows one to determine the absolute magnetic configuration, thus left-and right-handed helices can be easily distinguished [1]. On the other hand, knowing the magnetic configuration, one can analyse the polarization of a scattering beam [2]. Similar effects could also help to manipulate spin polarization of an electron current providing that the electrons interact with the known chiral magnetic structure.The ability to manipulate the electron spin is a necessary component for the spintronics [3], thus magnetic chiral organic molecules [4] or large scale magnetic structures have been proposed as such tools [5]. However, the question how to get the magnetic structure of a necessary chirality for spintronics applications is still open.Here we address the question for the case of Fe 1−x Co x Si solid solutions which, for certain compositions, show chiral (spiral) magnetic ordering [6][7][8].The structural chirality in monosilicides of 3d-metals is solely controlled by crystal growth [9]. A link between the structural and magnetic chiralities is provided by the Dzyaloshinskii-Moriya interaction (DMI) and has been experimentally proved for many monosilicides of 3dmetals [9][10][11][12].

Interface-induced phenomena in magnetism

“…Because of the nature of the symmetry breaking of an interface, interfacially-induced skyrmions are hedgehog (chiral Néel) type, while those in the B20 phase are vortex (chiral Bloch) type. Compositional control of B20 phase materials allows tuning of the size and sign of chirality of the Bloch vortex-type skyrmions [Shibata et al ., 2013; Siegfried et al ., 2015]; tuning of heterostructure parameters similarly control the size and chirality of the interface-induced Néel hedgehog-type [Chen et al ., 2013b]. Recent theoretical work looked at the competition between Rashba and Dresselhaus type spin-orbit coupling, and predicted complex phase diagrams of different types of non-collinear spin structures [Rowland et al ., 2016].…”

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

“…By changing the concentrations, T C changes from a few Kelvin to 50 K and the pitch from ∼30 to ∼200 nm [28,30]. Furthermore, the sign of the chirality alters from left to right handed at x = 0.65 [31].…”

Instantons in chiral magnets

“…The phase diagram in Fig. 1 with the variety of instantons can help us to understand physics which would be observed in future experiments on chiral magnets with controllable DM interaction [53][54][55][56] or easy-axis potential.…”