Speaker
Mr
Johan Cedervall
(Uppsala University)
Description
Permanent magnets are highly used in energy applications, both for harvesting in e.g windmills and for usage in electric vehicles [1]. To reduce the price tag for the manufactured magnets expensive elements like Nd, Gd and other rare earth elements should be avoided. Therefore other types of rare earth free permanent magnets are currently under heavy research. However, rare earth elements have a strong spin-orbit coupling with transition metals which gives the structures high magnetocrystalline anisotropy energy, a structural property that can give the material good magnetic properties. To overcome this without rare earth elements, uniaxial structures should be used, like tetragonal τ-phase MnAl or FeNi [2]. Another important application where magnetic materials will be used in the future is magnetic refrigeration, based on the magnetocaloric effect. An area of study where materials free from rare earth elements is investigated. A recently studied class of materials is the M5XB2 (M = Mn, Fe, Co and X = Si, P) a tetragonal system of compounds within the space group I4/mcm. Fe5SiB2 is one studied candidate that orders ferromagnetically at760K but lack magnetic hysteresis [3]. Theoretical predictions say that Co-substitutions will enhance the magnetocrystalline anisotropy which can make the compound a hard magnet. Due to thermodynamics, cobalt substitutions in Fe5SiB2 are impossible. Therefore, the proposed substitution has been studied for Fe5PB2 with diffraction, magnetometry, Mössbauer spectroscopy as well as DFT-calculations. It have been found that the cobalt atoms have a preference in site occupation in the structure, and that it effects the magnetic properties to such an extent that it becomes a candidate material for magnetic cooling instead of permanent magnets.
Primary author
Mr
Johan Cedervall
(Uppsala University)
