Magnetic properties of optimized cobalt nanospheres grown by Focused Electron Beam Induced Deposition (FEBID) on cantilever tips

TL;DR

This study investigates the magnetic properties of cobalt nanospheres grown by FEBID on cantilever tips, revealing optimal sizes and magnetic states for high-resolution MRFM applications.

Contribution

It provides the first comprehensive analysis of cobalt nanospheres grown by FEBID, highlighting their magnetic behavior and optimal dimensions for MRFM.

Findings

Cobalt content and magnetization decrease below 300 nm diameter.

Magnetic vortex state observed in remanence.

Optimal MRFM performance at ~200 nm diameter with high cobalt content.

Abstract

In this work, we present a detailed investigation of the magnetic properties of cobalt nanospheres grown on cantilever tips by Focused Electron Beam Induced Deposition (FEBID). The cantilevers are extremely soft and the cobalt nanospheres are optimized for Magnetic Resonance Force Microscopy (MRFM) experiments, which implies that the cobalt nanospheres must be as small as possible while bearing high saturation magnetization. It is found that the cobalt content and the corresponding saturation magnetization of the nanospheres decrease for nanosphere diameters below 300 nm. Electron holography measurements show the formation of a magnetic vortex state in remanence, which nicely agrees with magnetic hysteresis loops performed by local magnetometry showing negligible remanent magnetization. As investigated by local magnetometry, optimal behavior for high-resolution MRFM has been found for cobalt nanospheres with diameter of $\approx$ 200 nm, which present atomic cobalt content of $\approx$ 83 at% and saturation magnetization of 106 A/m, around 70% of the bulk value. These results represent the first comprehensive investigation of the magnetic properties of cobalt nanospheres grown by FEBID for application in MRFM.