The idea that it may be possible to change the magnetic polarisation of a material solely by the use of circularly-polarised photon pulses (rather than by applying a magnetic field) was first suggested in 2006.

The paper All-Optical Magnetic Recording with Circularly Polarized Light was published in the journal Physical Review Letters 99, 047601.

It described experiments with GdFeCo - an amorphous ferrimagnetic alloy that is widely used in magneto-optical recording - which was targeted with ultra-short pulses of polarised laser light. It was found that the laser pulses could flip the magnetic polarisation of the material.

The authors did not provide an explanation of the physical processes which could cause the changes. No explanation has yet been generally accepted.

Although experimentally demonstrated, the mechanism responsible for this all-optical magnetization reversal is not clear yet and remains a subject of debate.

Source : Wikipedia

If the effect can be broadly confirmed, it could open possibilities for extremely fast magneto-optical digital data recording.