Magnetometry with spin-based sensors

The summer intern will participate in a project aimed at using single defect centers in diamond to map out the magnetic fields generated by driven ferromagnetic circuits. Nanoscale magnetic circuits are critically important to computer hardware, especially in applications that use ferromagnetic domains to encode information. For example, magnetic random access memory (MRAM) could potentially replace standard DRAM while drastically reducing the demands for power. Understanding the dynamics of driven ferromagnetic circuits thus has important applications both in fundamental science and in industry. One challenge is to understand the role of spatial inhomogeneities, and one would thus seek to map out the magnetization of the device on the nanoscale – and ideally also watch its time evolution. However, there are few techniques that can measure magnetic fields with good sensitivity and excellent spatial and temporal (or, alternately, spectral) resolution.

One possibility is to fabricate the ferromagnetic circuit on the surface of a substrate embedded with tiny magnetic sensors. In particular, the nitrogen-vacancy (NV) defect center in diamond can be used to sense magnetic fields because its spin (which responds to magnetic fields) can be detected via the fluorescence intensity of the defect. Each defect can thereby reveal the magnetic field at its location, with the potential for nanoscale spatial resolution. Moreover, by manipulating the defect, one can select the time at which it senses the magnetic field or (more commonly) the frequency of magnetic fields that affect it. The central goal of this project is thus to use a diamond substrate embedded with NV centers to map out the driven dynamics of a ferromagnetic circuit fabricated on the diamond surface.

This project is in its initial stages, and the first goal for the project will be to observe resonant features in the circuit dynamics by correlating transport measurements (e.g. the resistance of the circuit as a function of the frequency of the AC current that drives it) with measurements of NV defects. Currently, we have begun implantation of defects into diamond substrates, and will begin fabrication of simple magnetic circuits this fall. Next summer, the first devices will likely be functional. The intern will help to push this project forward by developing a specific aspect of the apparatus or data analysis.

Faculty Supervisor:

Lilian Childress


Anchal Gupta



Physics / Astronomy



McGill University



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