Nano-scale traceable magnetic field measurements

Magnetic measurements are important to ensure device performance or correct battery placement in a range of modern technologies, including consumer electronics, induction chargers and electric cars. Many of these require magnetic field measurements at the micro or nanometre scale. Whilst techniques existed for measuring homogeneous fields at this level, none existed for spatially varying ones. Small, varying magnetic fields are not only weak, becoming weaker with increasing distance from a sample’s surface, but can also change direction and interact with other fields, complicating measurements.

One potential measurement solution was ‘Scanning Hall Microscopy’, which utilises a micro or nanometre sized semi-conductor sensor. The small sensor size and low measurement height avoids combining measurements over magnetic fields pointing in different directions. Hall sensors have a high spatial resolution, but lacked SI traceability at the required scale, restricting the uptake of this technique.

Building on the achievements of EMRP project SpinCal this project developed the first field sensors for calibrated imaging of magnetic systems at the centimetre and nanometre scale.

A scanning Hall probe microscope was established, demonstrating spatial resolution down to 5 µm with millimetre scan areas. In addition, a high-resolution scanning giant magneto resistance microscope was also developed, allowing spatial resolution down to 500 nm. To complete the required coverage for industrial use, a nano Hall mapper was also constructed and commercialised, allowing spatial resolution down to 10 µm and robust operation over centimetre scan areas.

As well as the instrumentation, the project developed the first ever reference samples for nano-scale Magnetic Field Measurement calibration, essential for verifying the performance of modern devices employing small, magnetic elements.

Project outputs included the publication of the first international standard for nano-scale magnetic measurements. To support the new standard, the guide ‘Guidelines for Nano-scale Magnetic Stray Field Measurements’ has been produced, along with the open access software Gwyddion, designed to help laboratory calibration measurements in support of the new standard.

The project’s magnetic force measurements have also been used in EMPIR project TOPS which investigated the potential of using electron ‘spin’ to process information, as ‘charge’ is used in traditional electronics to make faster, more efficient electronic devices.

The work of NanoMag will support a range of high-technology applications. This will increase the competitiveness of European industries in the field of nano-magnetic systems and devices and increase the reliability of nanomagnetic applications in areas such as health and biomedicine.

EMPIR project qMOIF builds on this work.