Microscopic origins and stability of the ferromagnetism in Co${}_3$Sn${}_2$S${}_2$

Abstract

Based on the density functional theory, we examine the origin of ferromagnetism in the Weyl semimetal Co${}_3$Sn${}_2$S${}_2$ using different types of response theories. We argue that the magnetism of Co${}_3$Sn${}_2$S${}_2$ has a dual nature and bears certain aspects of both itineracy and localization. On the one hand, the magnetism is soft, where the local magnetic moments strongly depend on temperature and the angles formed by these moments at different Co sites of the kagome lattice, as expected for itinerant magnets. On the other hand, the picture of localized spins still remains adequate for the description of the local stability of the ferromagnetic (FM) order with respect to the transversal spin fluctuations. For the latter purposes, we employ two approaches, which provide quite different pictures for interatomic exchange interactions: the regular magnetic force theorem and a formally exact theory based on the calculation of the inverse response function. The exact theory predicts Co${}_3$Sn${}_2$S${}_2$ to be a three-dimensional ferromagnet with the strongest interaction operating between next-nearest neighbors in the adjacent kagome planes. The ligand states are found to play a very important role by additionally stabilizing the FM order. When the local moments decrease, the interplane interactions sharply decrease, first causing the FM order to become quasi-two-dimensional, and then making it unstable with respect to the spin-spiral order propagating perpendicular to the kagome plane. The latter instability is partly contributed by the states at the Fermi surface and may be relevant to the magnetic behavior of Co${}_3$Sn${}_2$S${}_2$ near the Curie temperature. Peculiarities of the half-metallic ferromagnetism in Co${}_3$Sn${}_2$S${}_2$ are also discussed.

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Cited by in corpus (7)

• The magnetic structure of the topological semimetal Co${}_3$Sn${}_2$S${}_2$
• Linear response theories for interatomic exchange interactions
• The origin of ferromagnetic interactions in NaMnCl${}_3$: how the response theory reconciles with Goodenough-Kanamori-Anderson rules
• Unravelling the origin of the peculiar transition in the magnetically ordered phase of the Weyl semimetal Co3Sn2S2
• Exploring strong electronic correlations in the breathing kagome metal Fe${}_3$Sn
• Tunable Anomalous Hall Effect in a Kagome Ferromagnetic Weyl Semimetal
• NMR study of the local magnetic order in the kagome Weyl semimetal Co${}_3$Sn${}_2$S${}_2$