Conduction of spin currents through insulating antiferromagnetic oxides

¹ Service de Physique de l'État Condensé (CNRS URA 2464), CEA Saclay - 91191 Gif-sur-Yvette, France
² Institute of Physics, Kazan Federal University - Kazan 420008, Russian Federation
³ Université de Bretagne Occidentale, Laboratoire de Magnétisme de Bretagne CNRS - 6 Avenue Le Gorgeu, 29285 Brest, France

^(a) michel.viret@cea.fr

Received: 19 August 2014
Accepted: 22 November 2014

Abstract

Damping processes, associated to magnetization dynamics, allow to generate spin currents from precessing ferromagnets. These can be transmitted into adjacent conducting layers through an interface exchange interaction with conduction electrons. It is in principle also possible to inject angular momentum into insulators but the relevant physical mechanisms are not yet identified. In order to test some ideas concerning pure spin transport through insulating oxides, the present paper reports on the behaviour of two materials with very different properties: NiO is an antiferromagnet whereas SiO₂ is a non-magnetic light element insulator. While a sizeable flow of angular momentum is found to be able to propagate through nickel oxide, a SiO₂ layer as thin as 2 nm completely blocks this transfer. This underlines some essential features required to conduct a spin current, including the presence of either magnetic order through which magnons can propagate, or compounds with large spin-orbit interactions where phonons can carry angular momentum.