Scanning NV magnetometry of focused-electron-beam-deposited cobalt nanomagnets

TL;DR

This paper demonstrates the fabrication and magnetic characterization of cobalt nanomagnets created via focused-electron-beam deposition, revealing their magnetic properties and implications for spin qubit coherence.

Contribution

It introduces a method to fabricate cobalt nanomagnets with high magnetic quality and characterizes their stray fields using scanning NV magnetometry, linking fabrication to magnetic behavior.

Findings

Cobalt nanomagnets exhibit high saturation magnetization.

Magnetic domains and side-deposits are observed.

Estimated dephasing times indicate impact on spin qubits.

Abstract

Focused-electron-beam-induced deposition is a promising technique for patterning nanomagnets for spin qubit control in a single step. We fabricate cobalt nanomagnets in such a process, obtaining cobalt contents and saturation magnetizations comparable to or higher than those typically obtained using electron-beam lithography. We characterize the nanomagnets using transmission electron microscopy and image their stray magnetic field using scanning NV magnetometry, finding good agreement with micromagnetic simulations. The magnetometry reveals the presence of magnetic domains and halo side-deposits, which are common for this fabrication technique. Finally, we estimate dephasing times for electron spin qubits in the presence of disordered stray fields due to these side-deposits.