Helical structures in layered magnetic superconductors due to indirect exchange interactions mediated by interlayer tunneling

Abstract

Motivated by the recent discovery of helical magnetic structure in RbEuFe${}_4$As${}_4$, we investigate interlayer ordering of magnetic moments in materials composed of spatially-separated superconducting and ferromagnetically-aligned layers. We consider the interplay between the normal and superconducting indirect exchange interaction mediated by tunneling between the conducting layers. We elaborate a recipe to evaluate the normal interlayer interaction via two-dimensional density of states of an isolated layer and demonstrate that for bands with small fillings, such interaction is typically ferromagnetic and short-range. The nearest-layer interaction is proportional to the ratio of the interlayer hopping and in-plane band width squared. On the other hand, the superconducting contribution always gives antiferromagnetic interaction and may extend over several layers when the interlayer hopping energy exceeds the superconducting gap. The frustration caused by the interplay between the normal and superconducting parts may lead to spiral ground-state magnetic configuration. The four-fold in-plane anisotropy may lock the rotation angle between the moments in the neighboring layers to $90^{\circ }$, as it was observed in RbEuFe${}_4$As${}_4$

14 pages, 3 figures, subm. to Phys. Rev. B (29 AUG 2019)

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Cited by in corpus (11)

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• Superconductivity-driven ferromagnetism and spin manipulation using vortices in the magnetic superconductor EuRbFe4As4
• Topological magnetic order and superconductivity in EuRbFe${}_4$As${}_4$
• Long-range interaction of magnetic moments in a coupled system of S/F/S Josephson junctions with anomalous ground-state phase shift
• Novel magnetic stoichiometric superconductor EuRbFe4As4
• Controllable magnetic states in chains of coupled phi-0 Josephson junctions with ferromagnetic weak links
• Complex vortex-antivortex dynamics in the magnetic superconductor EuFe${}_2$(As${}_{0.7}$P${}_{0.3}$)${}_2$
• Effect of controlled artificial disorder on the magnetic properties of EuFe${}_2$(As${}_{1-x}$P${}_x$)${}_2$ ferromagnetic superconductor
• Evolution from helical to collinear ferromagnetic order of the Eu${}^{2+}$ spins in RbEu(Fe${}_{1-x}$Ni${}_x$)${}_4$As${}_4$
• Phenomenological theory of magnetic 90${}^{\circ }$ helical state
• Spin waves and high-frequency response in layered superconductors with helical magnetic structure