That sounds very wrong. Not a physicist, but light does not interact with magnets, or you need to get into the superconducting strength levels before it does.

https://en.m.wikipedia.org/wiki/Optical_rotation

It seems the optical rotation happens due to molecular structure of specific materials.

Edit, found this: https://en.wikipedia.org/wiki/Faraday_effect

So a specific material plus magnetic field is needed. But still not sure how strong of a field is sufficient.