Quantitative magnetic force microscopy on permalloy dots using an iron filled carbon nanotube probe

TL;DR

This paper introduces a new magnetic force microscopy probe based on an iron-filled carbon nanotube, enabling quantitative and high-resolution magnetic field gradient measurements on permalloy dots.

Contribution

The study develops and models a novel FeCNT-based MFM probe as a magnetic monopole, allowing precise quantitative magnetic measurements at nanoscale.

Findings

Accurate modeling of the FeCNT probe as a magnetic monopole.

Quantitative magnetic field gradient measurements near permalloy dots.

High lateral resolution of approximately 15 nm achieved.

Abstract

We have characterized a new Magnetic Force Microscopy (MFM) probe based on an iron filled carbon nanotube (FeCNT) using MFM imaging on permalloy (Py) disks saturated in a high magnetic field perpendicular to the disk plane. The experimental data are accurately modeled by describing the FeCNT probe as having a single magnetic monopole at its tip whose effective magnetic charge is determined by the diameter of the iron wire enclosed in the carbon nanotube and its saturation magnetization 4 \pi M_s ~ 2.2 x 10^4 G. A magnetic monopole probe enables quantitative measurements of the magnetic field gradient close to the sample surface. The lateral resolution is defined by the diameter of the iron wire ~15 nm and the probe-sample separation. As a demonstration, the magnetic field gradients close to the surface of a Py dot in domain and vortex states were imaged.