Researchers Identify Link between Magnetic Field Strength and Temperature

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Researchers from American Institute of Physics created crystals of silicon carbide to measure temperatures and magnetic fields at very small resolutions

The link between magnetic field strength and temperature helps to determine the temperature of a sample to a resolution of one cubic micron by measuring the field strength at which this effect occurs. Greater spatial resolution could benefit commercial and scientific pursuits as temperature sensing is integral in most industrial, electronics and chemical processes. Nitrogen atoms in diamonds can replace carbon atoms in vacancies of the crystal lattice. This formation offers useful quantum properties. These vacancies can have a negative or neutral charge and negatively charged vacancy centers are photoluminescent. Such vacancies produce a detectable glow when exposed to certain wavelengths of light. Moreover, a magnetic field can manipulate the spins of the electrons in these vacancies to alter the intensity of the photoluminescence.

Now, a team of Russian and German researchers created crystals of silicon carbide to measure temperatures and magnetic fields at very small resolutions. The diamond is centered by the crystals with vacancies similar to the nitrogen-vacancy. The silicon carbide is exposed to infrared laser light in the presence of a constant magnetic field to record the resulting photoluminescence. The research was published in AIP Advances on August 7, 2018.

The transfer between energy spin by electrons in the vacancies is eased by stronger magnetic fields. The proportion of electrons with spin 3/2 quickly changes at a specific field strength. The process is called anticrossing. The proportion of electrons in various spin states determine the brightness of the photoluminescence. The change in brightness allowed the researchers to gauge the strength of the magnetic field. Moreover, the electrons in the vacancies undergo cross-relaxation to abruptly change the luminescence. The process is characterized by one excited quantum system that shares energy with another system in its ground state, in order to bring both to an intermediate state. The temperature of a material determines the strength of the field needed to induce cross-relaxation. The researchers could calculate the temperature of the region of the crystal under investigation by varying the strength of the field and recording the incidences of change in photoluminescence. The researchers observed that the quantum effects remained even at room temperature.

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