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Nanomagnetism at NIST: Magnetic Nanoparticles
Magnetic nanoparticles have a number of applications due to their small size. One application is solid state refrigerants. The magnetocaloric effect, the coupling between magnetization and heat, is used to remove heat from a sample by cycling a magnetic field. The temperature range over which this cooling is effective is determined by the size of the magnetic moments. Nanostructured magnetic materials, in which the moments of many atoms are strongly coupled, provide a path for extending the effectiveness of this technique to higher temperatures.
There are several biological applications of magnetic nanoparticles, which can be injected into the human body because of their small size. They can be used as contrast agents in magnetic resonance imaging and to locally generate heat (hyperthermia) near cancer cells as a possible treatment for cancer. Programs at NIST are helping to determine the ultimate viability of these techniques by measuring the properties of these nanoparticles using a variety of techniques.
Small Angle Neutron Scattering (SANS) is a unique tool for measuring the properties of nanoparticles and particularly magnetic nanoparticles. Neutrons have a wavelength that is useful for scattering on the relevant length scales and polarized neutrons have good magnetic sensitivity.