Optimal design of nanomagnets for on-chip field gradients

TL;DR

This paper presents a systematic micromagnetic approach to designing nanomagnets that generate optimal localized magnetic field gradients for spin qubit applications, moving beyond empirical methods.

Contribution

It introduces a general optimization framework for nanomagnet design based on micromagnetic simulations, identifying geometries that produce maximum field gradients.

Findings

Identified optimal ferromagnetic geometries for maximum field gradients.

Determined minimum saturation requirements for nanomagnet operation.

Provided guidelines for material selection based on external field strengths.

Abstract

The generation of localized magnetic field gradients by on-chip nanomagnets is important for a variety of technological applications, in particular for spin qubits. To advance beyond the empirical design of these nanomagnets, we propose a systematic and general approach based on the micromagnetic formulation of an optimal field gradient source. We study the different field configurations that can be realized and find out quantitatively the most suitable ferromagnetic layer geometries. Using micromagnetic simulations, we then investigate the minimum requirements for reaching magnetic saturation in these nanomagnets. In terms of either longitudinal or transverse field gradient, the results provide an optimal solution for uniform, saturated nanomagnets, where the magnetic material can be selected according to the strength of the external fields that can be used.