Resetting the magnetization of assemblies of nanoparticles with Microwaves

It is shown that in materials containing magnetic nanoparticles it is possible to reset the magnetization with negligible heating of the material, provided that sufficient microwave power is available. The process involves the decay of a microwave photon and creation of two magnons of equal and opposite wave-vector. As such it requires relatively high microwave frequencies, e.g. a 30 nm diameter Ferrite particle requires 24 GHz, because, with the exception of the uniform mode, lower frequency magnons are forbidden since their wave-length would exceed twice the diameter of the particle.