What is "photomagnetism"

Photomagnetism \Pho`to*mag"net*ism\, n. The branch of science which treats of the relation of magnetism to light.

n. The branch of science that deals with the relation of magnetism to light.

The photomagnetic effect is the effect in which a material acquires (and in some cases loses) its ferromagnetic properties in response to light. The current model for this phenomenon is a light induced electron transfer, accompanied by the reversal of the spin direction of an electron. This leads to an increase in spin concentration, causing the magnetic transition. Currently the effect is only observed to persist (for any significant time) at very low temperature. But at temperatures such as 5K, the effect may persist for several days.