In-Situ Switching of Tip Magnetization to Eliminate Topographic Effects in MFM Measurements

Topics Covered

Introduction
NanoScan VLS-80 Microscope
Observations from MFM Data
About NanoScan

Introduction

The article focuses on eliminating topographic effects in magnetic force microscopy (MFM) measurements by switching the tip magnetization in order to differentiate between magnetism and topography.

NanoScan VLS-80 Microscope

The NanoScan VLS-80 microscope comprises built-in permanent magnets on which the tip is precisely placed to enable switching the magnetization. Care is taken not to disturb the sample or break the vacuum. The magnets are placed in such a manner to prevent disturbance of the samples.

As the tip magnetization is controlled by a software, the switching happens in a few seconds. Then the tip is placed back on the imaging area with a precision better than 1µm.

Observations from MFM Data

The MFM data of bit-patterned media with a 200nm pitch displays perpendicular magnetic anisotropy. The two pictures display the magnetization of the islands prior to and after switching the tip magnetization (Figure 1).

Figure 1. hr-MFM images of bit-patterned media with a pitch of 200nm. The upper image shows the magnetic signal with tip magnetized up and the lower image shows the same area after switching the direction of the tip magnetization. Red/ blue contrast refers to the tip and sample magnetization being anti-parallel/parallel.

From the two images, it can be observed that the island contrast is reversed, thereby establishing that the signal is magnetic and that topographic contributions can be eliminated.

The mode of measurement is high-resolution MFM, which is a non-contact type of MFM. Another observation on the contrasts seen in the picture is that the cantiliever resonance shows a frequency shift due to the contact between the sample magnetic stray fields and the tip.

Additionally, a linear encoder is used during the switching process to precisely assess the height of the tip. This enables properly defined magnetic fields of both polarities to be applied to the tip.

About NanoScan

With excellent know-how in the fast growing field of nanoscience, the main focus of NanoScan AG is on research and development of high-resolution and versatile magnetic and non-contact scanning force microscopes. These instruments are especially designed to fulfill the present and future analytical needs on nanometer-sized surface structures.

This information has been sourced, reviewed and adapted from materials provided by NanoScan AG.

For more information on this source, please visit NanoScan AG.

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