Magnetization and MR

Magnetism is a natural property of nearly all substances. Magnetism in typical ferrous magnets arises due to alignment of the electron orbits of iron atoms. Nuclear magnetism is also achieved naturally through alignment of nuclei in a magnetic field. Furthermore, magnetized nuclei behave like gyroscopes, if tipped they will undergo precession around their original direction. Subjecting them to radio waves at their characteristic frequency disturbs their equilibrium orientation and causes them to precess. When they are precessing, they emit faint radio waves at this frequency. This phenomenon is nuclear Magnetic Resonance or MR.

We achieve much higher levels of nuclear magnetism by technological means. Lasers can be used to control and manipulate the alignment of electrons in atoms. These electrons can then exert a torque on noble gas nuclei such as xenon or helium far greater than that of magnetic fields. We use lasers to create an environment where these nuclei are forced to align. They produce magnetism that is enhanced by a factor of one hundred thousand over what could be obtained in strong magnetic fields. Note that this magnetism is nevertheless far smaller than the smallest refrigerator magnet, undetectable without magnetic resonance techniques, and totally harmless.