Laurence Eaves, Peter King, and their colleagues explain that so-called diamagnetic materials tend to become magnetized in a direction opposite to the magnetic field being applied to them. Magnetic levitation occurs when the force on such an object is strong enough to balance the weight of the object itself. If the object is immersed in a fluid such as gaseous oxygen, the levitation can be enhanced by the effect of buoyancy caused by the “magneto-Archimedes” effect.
Liquid oxygen is magnetic but highly combustible. So the Nottingham team has used a safer mixture of liquid nitrogen and oxygen, and found the optimum mixture for floating heavy objects in safety, making possible commercial applications of this technology, such as separating diamonds from rock.
King explains: “You can use this technology to accurately sort minerals. Under vibration you throw crushed ore into the air and in the magnet the different components experience different effective gravity. They therefore tend to land at different times and after a short while the vibration sorts them into bands according to their density. The method can discriminate between components with very small differences in density enabling you to extract the precious parts you require.”
Adapted by David Bradley Science Writer from an Institute of Physics press release.