Patent ID: 7273580

Claim:
A process for heating a substrate which contains—based on the total weight of the substrate—0.1 to 70% by weight of metallic, magnetic, ferrimagnetic, ferromagnetic, antiferromagnetic or superparamagnetic particles, said particles having an average particle size of 1 to 5,000 nm, comprising simultaneously exposing the substrate to electromagnetic radiation comprising microwave radiation and a direct current magnetic field, wherein the direct magnetic field excites ferromagnetic resonance modes in said particles to convert the microwave radiation into heat, wherein the strength of the direct current magnetic field, H dc , is selected according to the formula f=γμ 0 ( H dc +H A +q m M s ) wherein f is the microwave frequency, γ is the gyromagnetic constant, μ 0 is the permeability of free space, H A is the specific magnetic crystal anisotropy field of the nanoparticles, q m is the geometric factor specific to the excited ferromagnetic resonance modes, and M s is the saturation magnetization of the excited ferromagnetic resonance modes.