Kapitsa pendulum effects in Josephson junction + nanomagnet under external periodic drive

TL;DR

This paper explores how high-frequency external periodic drives can reorient a nanomagnet coupled to a Josephson junction, using the Kapitsa pendulum as an analog, and provides analytical formulas for stable magnetic orientations.

Contribution

It introduces a novel analogy between the Kapitsa pendulum and nanomagnet dynamics in Josephson junctions, deriving analytical expressions for magnetic reorientation under periodic drive.

Findings

High-frequency oscillations induce reorientation of the nanomagnet's easy axis.

The magnetic field from the Josephson junction influences the frequency-dependent orientation.

Analytical formulas for stable magnetic positions are derived.

Abstract

We investigate reorientation effects under external periodic drive in the nanomagnet dynamics coupled to a Josephson junction. The Kapitsa pendulum is introduced as a mechanical analog to this system and we demonstrate the reorientation of the easy axis of the nanomagnet. The magnetic field generated by the Josephson junction and external drive plays the role of the oscillating force of the suspension point in the Kapitsa pendulum. The high frequency oscillations change the orientation of the magnetic moment. The magnetic field of the quasiparticle current determines the frequency dependence of the magnetic moment's orientation. We obtain simple analytical formulas for the stable position of the magnetic moment, both under the external periodic drive and without it. The influence of external periodic drive on the voltage of complete reorientation have been demonstrated.