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New findings to create better permanent magnet

Magnets are atomic powered. The classical explanation of the phenomenon is based on the electron spin alignment. Permanent magnets have their spin aligned all the time while temporary magnets have their spin aligned only under the influence of a strong external magnetic field. However, this explanation is only partial and science has still difficulties to explain where the energy for this strong field comes from. You can find an interesting explanation by Richard Feynman (Nobel Prize in Physics in 1965) in the video below.

While theoretical physicist still struggle to find a suitable equation for the phenomenon, applied physicists are working on ways to improve magnets. To obtain a good permanent magnet you should have a high magnetic field with a low mass, and a stable material resisting against the influences which would demagnetize it. The best alloy used for these permanent magnet is the SmCo5 formulation. This material is almost as strong as more modern neodymium magnets but has a better stability against temperature.

One way to improve the alloy SmCo5 is to increase its magnetic strength by replacing cobalt with iron (SmCo5 > SmFe5). However, substituting all cobalt atoms for iron, which has a larger magnetic moment, creates an unstable structure for the material. A solution seems to use instead a mix of Nickel and Iron.

In a recent work, a team from the Lawrence Livermore National Laboratory from California proposed a new efficient permanent magnet, SmCoNiFe3. Using first-principles electronic-structure calculations, the team found that their new alloy has very promising magnetic properties and could replace SmCo5 or neodymium magnets in various applications.

Calculated (black circles) and experimental (red squares) formation energies (eV/cell). The red dashed line is an extrapolation. Negative energies indicate thermodynamic stability.

Their new magnet removes most of the disadvantage of SmCo5 while preserving its superior high-temperature efficiency over the neodymium magnets. They showed shown that substituting most of the cobalt with iron in SmCo5 and doping with a small amount of nickel results in a new permanent magnet. Their numerical calculation predicted exceptional magnetic properties.

"This is a very timely discovery because the cobalt prices are up and have nearly doubled this year because of the anticipated demand for lithium-ion-cobalt batteries. Iron, on the other hand, is abundant and very inexpensive."

Per Soderlind, Lawrence Livermore National Laboratory, California

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