Spin superfluidity on the spherical surface

• Published in: Journal of magnetism and magnetic materials 2022-05, Vol.550, p.169033, Article 169033
• Main Authors: Sousa, G.J., Moura, A.R.
• Format: Article
• Language: English
• Subjects: Circuits; Curved space; Damping; Ferromagnetism; Flat surfaces; Fluids; Magnetism; Magnetization; Magnons; North Pole; South Pole; Spherical shells; Spin superfluidity; Spin valves; Spintronics; Superfluidity
• ISSN: 0304-8853; 1873-4766
• DOI: 10.1016/j.jmmm.2022.169033

Spintronics on flat surfaces has been investigated over the years, and the scenario is relatively well-known; however, there is a lack of information when considering non-flat geometries. In this paper, we are interested in the spin current on the spherical surface of a ferromagnetic insulator. We are mainly concerned with the superfluid spin current transport when spin current is injected at the north pole and propagates to the south pole. We evaluate the spin transport over the spherical surface using the magnetoelectric circuit theory and the semiclassical magnetization formalism. Including the magnetization damping by the Landau–Lifshitz–Gilbert equation, we obtain a spin current that propagates over distances larger than the magnon ballistic decay length, evidence of spin superfluidity. In addition, provided that the ejected spin current is always radially aligned, along with the dissipationless nature, a spherical shell could be used as an efficient oriented spin valve. •The dissipation is investigated by the covariant LLG equation.•The spin superfluidity on the spherical surface is determined.•The magnetization dynamics of spherical shells is obtained.•A reorienting spin current device is suggested.