New Way to Excite Tiny Diamonds can Create Magnetic Sensing Devices

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New sensor device could replace difficult-to-use sensors in applications from navigation to medical imaging

UC Berkeley engineers have created a device that reduces the energy needed to power magnetic field detectors. It is predicted to revolutionise how you measure the magnetic fields that flow through your electronics, your planet, and your bodies.

Each time a diamond-based sensor measures a magnetic field, it must first be blasted with one watt to ten watts of microwave radiation to prime it to be sensitive to magnetic fields. The researchers excite tiny diamonds with microwaves using 1000 times less power, making it feasible to create magnetic-sensing devices that can fit into electronics like cell phones.

Replacing carbon atoms with nitrogen atoms

Bombarding a diamond with a jet of nitrogen gas can knock out some of its carbon atoms, replacing them with nitrogen atoms. These nitrogen interlopers called nitrogen-vacancy (NV) centres.

To detect magnetic fields, scientists first hit the NV centres with high-powered microwave radiation, equal to about one-hundredth the power of your standard microwave. They then illuminate the NV centres with a laser which is absorbed and emitted by the nitrogen atoms.
Well, the strength of the magnetic field is related to the strength of the emitted laser light.

Moreover, the intensity of the emitted light can be used to measure the field strength.
To create the device, the researchers placed diamond nanocrystals containing thousands of NV centres piece onto a film called a multiferroic. This new type of material is capable of transferring microwave energy to the crystals.

Imaging inside the body and under the earth

Medical applications of magnetic sensors include magnetoencephalography which uses magnetic fields to measure brain waves. Second application is magnetocardiography which uses magnetic fields to image heart function.
The sensors could also be placed in planes or drones to aid in spotting rare earth metals underground or used in cell phones to improve navigation. Magnetic field detection is just one application of NV centres. The team is planning to refine their technology to use NV centres and other types of quantum systems in a wide variety of applications.