Linear magnetic flux amplifier

TL;DR

This paper demonstrates a linear magnetic flux amplifier using a superconducting loop with a Permalloy magnetic dot, showing tunable flux gain and enhanced sensitivity through controlled magnetization rotation.

Contribution

It introduces a novel design for a linear magnetic flux amplifier utilizing a Permalloy dot to achieve tunable flux gain in superconducting quantum interference devices.

Findings

Flux gain can be tuned by adjusting dot dimensions.

Magnetization coherently rotates with applied magnetic field.

Enhanced sensitivity in superconducting quantum interference devices.

Abstract

By measuring the critical current versus the applied magnetic field $I_c(\Phi)$ of an Al superconducting loop enclosing a soft Permalloy magnetic dot, we demonstrate that it is feasible to design a linear magnetic flux amplifier for applications in superconducting quantum interference devices. The selected dimensions of a single-domain Permalloy dot provide that the preferential orientation of the magnetization is rotated from the perpendicular direction. By increasing an applied magnetic field, the magnetization of the dot coherently rotates towards the out-of-plane direction, thus providing a flux gain and an enhancement of the sensitivity. As a result of a pronounced shape anisotropy, the flux gain generated by the dot can be tuned by adjusting the dimensions of the dot.