Why is it important to find an alternative to rare earth metals?
Rare earth metals are relatively scarce and difficult to mine; there is a serious concern that the demand will outgrow the production in the coming years.
Furthermore, the extraction, processing and recycling of these heavy metals pose serious environmental hazards.
Which metals can be made magnetic using this method?
We don’t know yet, but at least all transition metals are candidates to become magnetic using this method.
Currently, only three metals are ferromagnetic at room temperature: iron, cobalt and nickel, so at the very least we should be able to widen the choice.
What is the Stoner Criterion?
The Stoner criterion is a simple equation to determine if a metal will be ferromagnetic or not based on the product of two physical properties: the density of states at the Fermi level and the exchange interaction.
The first one tells us how many states are available to electrons at their highest energy and the second quantifies the interaction between their angular momenta or spins. If the product of these two parameters is higher than one, the metal will be ferromagnetic.
How are electrons removed from the atoms?
The electrons are ‘sucked’ from the metallic reservoir by the semiconducting molecules because these have a large electron affinity.
Can this process be carried out on a large scale?
Currently, this is a surface effect. It could be implemented on a large scale in thin films (e.g. wafers etc.), but not in bulk – at least not yet.
What further work is required to bring this technique to industry?
We need to make the effect much stronger, increasing the emergent magnetisation and the magnetic anisotropy in the metal, that is, we need to make the hysteresis loops taller, wider and squarer. Then, we need to find a process to replicate the effect in large volumes.
Will these types of magnets have properties or applications that differ from existing magnetic materials?
Potentially, they could have very different properties and/or applications. For example, we could use it to make non-corrosive magnetic metals for outdoor applications, to recycle and recover precious materials, and in magnetic semiconducting interfaces for computing etc.
About Dr. Oscar Cespedes
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Dr. Oscar Cespedes graduated from the University of Zaragoza (Spain) in 2000, having completed a final year project in electron-magnon interactions at the National Laboratory of Intense Magnetic Fields (LNCMI) in Toulouse (France).
He then joined the Physics Department at Trinity College, Dublin to work under the supervision of Prof. JMD Coey. The title of his PhD thesis was “Spin Transport in Magnetic Nanostructures”. After his doctorate, he took a position as a research engineer at the Atomic Energy Commission of France (CEA-Saclay), developing atomic-scale spintronic devices.
In 2006, he moved to Kyushu University (Fukuoka, Japan) to investigate the biomedical effects of radiofrequency magnetic fields. In the following year, he received a fellowship from the Japan Society for the Promotion of Science to pioneer magnetic therapies in Alzheimer’s disease. Since 2009, Dr. Cespedes has been a lecturer at the School of Physics & Astronomy of the University of Leeds, where he leads novel research in molecular magnetism and spintronics.
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