# Moment switching in nanotube magnetic force probes

## TL;DR

This paper explains the phenomenon of spatial frequency doubling in magnetic force microscopy using nanotube tips, attributing it to magnetic moment switching, and suggests potential for imaging higher data densities.

## Contribution

It demonstrates that moment switching causes frequency doubling in nanotube MFM tips and models the involved volume, indicating potential for higher density magnetic imaging.

## Key findings

- Frequency doubling is due to nanotube tip moment switching.
- Model shows a significant volume involved in switching.
- Potential for imaging very high bit densities.

## Abstract

A recent advance in improving the spatial resolution of magnetic force microscopy (MFM) uses as sensor tips carbon nanotubes grown at the apex of conventional silicon cantilever pyramids and coated with a thin ferromagnetic layer. Magnetic images of high density vertically recorded media using these tips exhibit a doubling of the spatial frequency under some conditions. Here we demonstrate that this spatial frequency doubling is due to the switching of the moment direction of the nanotube tip. This results in a signal which is proportional to the absolute value of the signal normally observed in MFM. Our modeling indicates that a significant fraction of the tip volume is involved in the observed switching, and that it should be possible to image very high bit densities with nanotube magnetic force sensors.