Buckyballs Induce Magnetism In Copper And Manganese

Only iron, cobalt, and nickel are permanently magnetic at room temperature, a property known as ferromagnetism that stems from how valence electrons are distributed and interact with each other within the metal. To develop or improve applications that use magnetism, such as computer memory and power generation, researchers would like to induce the property in other elements. Layering C₆₀ on thin films of either copper or manganese successfully makes the metal layers ferromagnetic, reports a team led by Oscar Cespedes of the University of Leeds, in England (Nature 2015, DOI: 10.1038/nature14621). The magnetization arises from electron transfer from the metal to C₆₀, and it’s not limited to layering with buckyballs, Cespedes notes. Other materials with high electron affinity, as well as other metals, will also work. The effect depends on the thickness of the layers: The copper layer must be 2 to 3 nm thick, the manganese layer 2 to 15 nm thick, and the C₆₀ layer 10 to 20 nm thick. The metal’s nonmagnetic bulk properties take over if the layers are too thick, and the magnetization drops off if the assemblies oxidize.