Project outline

Need of the Joint Research Project:

Macroscopic magnetic field measurements are traceable to nuclear magnetic resonance (NMR) quantum standards and traceability chains to industry are well established. These calibration chains however only relate to measurements of fields that are constant and homogeneous over macroscopic volumes or surface areas down to the millimetre scale. Important European high tech industries such as magnetic sensor manufacturing, precision position control and sensing in industrial applications, information technology, and bio-medical applications as well as R&D laboratories, require traceable and reliable measurements of magnetic fields and flux densities on the micro- or nanometre scale e.g. for quantitative analysis and quality control.

Three measurement techniques: 1) scanning magnetic field microscopy and 2) magneto optical indicator film (MOIF) microscopy to measure and image magnetic stray field distributions on the micrometre scale together with 3) magnetic force microscopy (MFM) for nano magnetic imaging, have been established, but standards for traceable calibrations for these three techniques are currently unavailable.

The project’s objectives are:

1. To provide metrology tools and methods based on scanning magnetic field microscopy techniques suitable for traceable measurements of the local stray field distribution of permanent magnets and magnetic encoder scales with spatial resolution from 50 μm down to 500 nm; to evaluate the measurement techniques with respect to traceability and uncertainties; and to establish traceability of the local stray field measurements to macroscopic SI standards and to evaluate their uncertainties.

2. To provide metrology tools and methods based on magneto optical indicator film (MOIF) microscopy techniques suitable for traceable measurements of the local stray field distribution of permanent magnets and magnetic encoder scales with spatial resolution from 50 μm down to 500 nm; to evaluate the measurement techniques with respect to traceability and uncertainties; and to establish traceability of the local stray field measurements to macroscopic SI standards and to evaluate their uncertainties.

3. To provide validated calibration techniques to ensure SI traceability of magnetic force microscopy (MFM) with spatial resolution below 50 nm; to develop, test and validate different calibration approaches; to establish traceability to macroscopic SI standards and to evaluate their uncertainties.

4. To provide calibration artefacts suitable for traceable on-site calibrations to underpin the reliability of micro- and nano-scale traceable magnetic field measurements by end-users.

5. To facilitate the uptake of new advanced high resolution magnetic field metrology techniques by the measurement supply chain, ensuring traceability of measurement results to the users of metrology services and to contribute to the development of standards by the international (IEC) standardisation committees concerning nano-scale magnetic measurements or nano-electronics.

Progress beyond the state of the art:

In terms of macroscopic scales magnetic field measurements are traceable to NMR-based SI standards and traceable calibration chains to the end-users are well established, however, such calibration chains do not exist on the micrometre and nanometre scale. This project will go beyond the state of the art by providing tools and methods for traceable measurements and calibrations of magnetic fields with micro or nano-scale spatial resolution and by traceably connecting high resolution field measurements to the macroscopic SI standards.

The project will provide and validate high resolution scanning field microscopy with spatial resolution from 50 μm down to 50 nm and a European scanning magnetic field metrology infrastructure with full dimensional traceability. Furthermore new calibration techniques will be developed and validated that take into account local field variations on the length scales of the sensor diameter. In addition the project will develop and validate calibration techniques for MOIF microscopy that take into account local vector stray field variations over the MOIF film thickness and will develop a validated European metrology infrastructure for traceable MOIF measurements with optical resolution down to 500 nm.

MFM can be considered the standard tool for nano scale investigations of the local magnetic properties of magnetic nanostructures, thin films and devices. Although various approaches for traceable MFM calibrations have been described in literature no established and validated path for traceability of end-user MFM measurements is available. Therefore the project will develop, compare, and validate complementary MFM calibration schemes based on nano scale stray field materials, planar field coils, and measurements of the tip stray field by nano Hall sensors, all supported by suitable numerical modelling.

To underpin harmonisation of measurements the project will develop “Guidelines for Traceable Nano scale Magnetic Field Measurements” from the results of a round robin comparison of spatially resolved field measurements conducted within the project. Based on the Guidelines the consortium aims to lead a project team of IEC TC113 “Nanotechnology standardisation for electrical and electronic products and systems” to develop a Technical Specification (TS) for a standard on: “Spatially resolved local magnetic field measurements on the micrometre and nanometre scale”.