Abstract: The present invention provides a method for producing a magnetic nanoparticle-coated laminate material. The method comprises coating a pair of opposed surfaces of a plurality of steel or iron/cobalt (Fe/Co) alloy film portions with a magnetic nanoparticle-containing coating. Each magnetic nanoparticle comprises a core and a shell covering at least a portion of the core. The shell and core are made of different materials selected from one or more of: iron, cobalt, nickel; and/or alloys comprising two or more of: iron, cobalt and/or nickel; and/or magnetic rare earth metals; and/or diamagnetic transition metals. The method further comprises stacking the coated film portions on top of each other such that a or each coated surface of each film portion is located adjacent a further coated surface of an adjacent film portion; and compressing the stacked coated film portions together to form a nanoparticle-coated laminate material.