Current-induced switching in a magnetic insulator
November 23, 2016
Nature Magazine published a paper written by Prof. Geoffrey Beach and his collaborator Prof. Caroline Ross who have shown that a pure spin current can be injected into in an electrically insulating material, and be used to switch its magnetization direction.
This is striking because, in conventional spintronic materials, spin currents are generated by lining up the spins of the electrons that conduct a current, so when a charge current flows, a spin current flows along with it. But the two (charge and spin) are coupled, and neither can flow without the other. In their paper, they reveal experimentally a remarkable and technologically useful behavior: when a metallic conductor is placed in contact with the insulating magnetic material, a charge current flowing in the metal pumps a spin current into the insulator – in other words, the spin of the electrons is transmitted into a material in which the electron itself cannot propagate. They also show that a reverse effect can also occur – the electrical conductivity of the metal layer depends on the orientation of the magnetic poles of the insulator. Remarkably, even though electrons flowing through the metal cannot propagate into the insulator, they can still ‘sense’ its magnetic orientation. The practical implication is then that it is possible to electrically write and read the magnetic state in an insulating material, which has great consequence for spin-based data storage and logic.