Modeling and limits of advanced HT-magnets

This paper combines microstructural investigations using transmission electron microscopy with micromagnetic finite element simulation of the magnetic domain wall pinning behavior of novel Sm(Co, Fe, Cu, Zr)_{7, 4-8}, ₀ permanent magnet materials applicable up to 550°C. A finite element method was used to simulate domain wall pinning in SmCo₅/Sm₂Co₁₇ based permanent magnets. The finite element model was built-according to the cellular microstructure obtained from TEM investigations. The numerical results show a strong influence of the dimension of the cell boundary phase on the coercive field, which significantly increases with the extension of the 1:5/7-type cell boundary phase. The calculated values of the coercive field are in the range from 1000-2000 kA/m assuming a cell size varying from 80-160 nn. The difference of the magnetocrystalline anisotropy between cell boundary and cell interior phases is determined by the Cu-content of the magnet. Due to the lower Curie temperature of the Cu-containing cell boundary phase high coercive fields are obtained at elevated temperatures (>400°C)