Quantum-calibrated magnetic force microscopy
More reliable magnetic field measurements in the nanometer range
To develop future magnetic components such as sensors and data storage devices, industry needs traceable magnetic field measuring systems with the best possible spatial resolution. The most widespread method for measuring magnetic field distributions on the nanometer scale is magnetic force microscopy (MFM). In MFM, a magnetic tip is moved a few nanometers above a sample surface while measuring the force which acts on the tip in the magnetic field of the sample. To be able to calculate the magnetic field strength from this force in SI units, the magnetic properties of the tip must be known very accurately. For this purpose, simplifying models combined with measurements on magnetic reference samples have been used to date.
Within the scope of a cooperation project between PTB and the University of Ulm, the magnetic properties of such a magnetic tip have now been characterized precisely for the first time by means of a quantum sensor. This nitrogen vacancy (NV) center sensor consists of a single atomic lattice defect in a diamond crystal whose optical spectrum depends on the external magnetic field. In the experiments performed, the magnetic tip was scanned in a plane over the NV center, and the optical spectrum was measured at each point. Based on these measurements, a map of the magnetic field emanating from the tip was derived. The tip’s magnetic properties that are relevant to magnetic force microscopy were then determined from this map. After this procedure, the tip was quantum calibrated and could be used for precise and reliable magnetic field measurements on the nanoscale.
In further investigations, it is also planned to set up such a measuring system to characterize MFM tips at PTB. In this way, it would be possible to perform MFM measurements using quantum-calibrated tips directly at PTB in the future.
Contact
Hans Werner Schumacher
Department 2.5
Semiconductor Physics and Magnetism
Phone: +49 531 592-2500
hans.w.schumacher(at)ptb.de
Scientific publication
B. Sakar, Y. Liu, S. Sievers, V. Neu, J. Lang, C. Osterkamp, M. L. Markham, O. Öztürk, F. Jelezko, H. W. Schumacher: Quantum calibrated magnetic force microscopy. Phys. Rev. B, 104, 214427 (2021)