Magnonic control of the superconducting spin valve by magnetization reorientation in a helimagnet
We propose a method to control a bilayer superconducting spin valve (SSV) which does not perturb its superconducting state and is suitable for energy saving cryogenic electronics. This SSV consists of a superconducting layer and a helimagnetic layer of B20 family compounds, namely, Nb and spiral antiferromagnet MnSi. Thanks to unique properties of MnSi—broken inversion symmetry and cubic crystal lattice — there are a few ground state magnetic configurations with different directions of the magnetic spiral, divided by a potential barrier.
Superconductivity in such a bilayer is controlled by the reorientation of the spiral vector in the MnSi layer, which leads to a change in the critical temperature of the Nb layer due to the proximity effect. The switching is proposed to be carried out by a several hundred ps in duration magnetic field pulse of several kOe in magnitude. Such a pulse does not destroy the superconducting state of the Nb layer by itself but leads to the excitation of magnons in the MnSi layer, which triggers the reorientation process of the magnetic spiral. After the completion of this process, the Nb layer switches into a normal state. Inverse switching returns the spiral to the initial state, opening the valve and turning
on the superconducting state. The system can be switched there and back by a magnetic field of opposite signs along one direction in the layers plane, which allows an easy control. The switching time is estimated as several nanoseconds, which coincides with the scales of the STT-MRAM recording time.