
DOI:	10.7795/720.20200610
title:	Round robin comparison on quantitative nanometer scale magnetic field measurements by magnetic force microscopy

summary: As a standard tool for nano-scale investigation of magnetic domain structures, magnetic force microscopy (MFM) measures the local stray magnetic field landscape of the measured sample, however, generally providing only qualitative data. To quantify the stray magnetic fields, the MFM system could be calibrated by a so-called transfer function (TF) approach which fully considers the finite extent of the MFM tip. However, albeit being comprehensive, the TF approach is not yet well established, mainly due to the ambiguities concerning the input parameters and the measurement procedure. Additionally, the calibration process represents an ill-posed problem which requires a regularization that introduces further parameters. In this paper we propose a guideline for quantitative stray field measurements by standard MFM tools in ambient conditions. All steps of the measurement and calibration procedure are detailed, including reference sample and sample under test (SUT) measurements and the data analysis. The suitability of the reference sample used in the present work for calibrated measurements on a sub-micron scale is discussed. A specific regularization approach based on a Pseudo-Wiener Filter is applied and combined with criteria for the numerical determination of a unique regularization parameter. To demonstrate the robustness of such a defined approach, a round robin comparison of calibrated MFM measurements between four labs, CMI, PTB, IFW, and NPL has been presented. The results of three participating labs were compared, showing a good consistency of measured stray field values, independent on the tips, equipment and operator. This proves the robustness of the described TF approach when the detailed measurement procedure as described above is followed. The remaining issues have been discussed for further improving the measurement and data analysis protocol. The results support the establishment of a standardized method for quantitative nanometer scale stray field measurement by standard magnetic force microscopy in ambient conditions.

creators: Xiukun Hu, AG 5.23 3D Nanometrologie

license:  CC BY 4.0 International

keywords: Comparison, Quantitative magnetic force microscopy, Magnetic probe calibration, Reference sample, Stray magnetic field

classification: INSPEC A0620H, INSPEC A0779, INSPEC A6116P, INSPEC B7130, INSPEC B7200, INSPEC E1650
project title:	Nano-scale traceable magnetic field measurements
funder:	European Metrology Programme for Innovation and Research (EMPIR)
funder nr: 15SIB06	
link to projekt homepage: https://www.ptb.de/empir/15sib06-home.html
related objects: https://doi.org/10.1016/j.jmmm.2020.166947, ISSN: 0304-8853
software:
description of the individual files: 
-The folder names ('Fig') repreasent the data used in the corresponding figures in the paper doi.org/10.1016/j.jmmm.2020.166947. Each folder includes the MFM data (named with 'Phase') and calibrated stray field data (named with 'Hz') from 4 particpated laboratories, and two theoretically calculated data (named with 'cal'). The detailed infomation can be found in the published paper. 
-The folder named as 'Reference sample S0 MFM data' includes the MFM Phase data measured on the reference sample S0 from 4 participating labs. 
-Each '.dat' file includes three columns, representing the position coordinates x, y (in µm) as well as one between phase (in degrees), vertical magnetic field (in A/m) or vertical magnetization (in A/m), respectively.
