1) Type of magnet 
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 m...
• (n.) The branch of science which treats of the relation of magnetism to light.
Pho`to·mag'net·ism noun The branch of science which treats of the relation of magnetism to light. 
photomagnetism Magnetism induced by the action of light.