Trends in magnetism and magnetic anisotropy of RCo₅ materials

The RCo₅ family of materials (R = rare earth) are integral to many permanent magnet applications due to their high paramagnetic to ferromagnetic transition (Curie temperature) and potentially high magneto-crystalline anisotropy energy (MAE). These properties make them very attractive for sensitive industrial applications where other permanent magnets fail. We assess all the RCo₅ systems within the advanced density function theory (that incorporates onsite electron correlation and spin orbit coupling models) framework by calculating their MAE, magnetic moments, and Curie temperatures. We review experimental anisotropy data and do simple machine learning modeling for first order anisotropy constants at low temperature. We find NdCo₅ and SmCo₅ with planar (non-useful) and uniaxial (useful) magnetic anisotropy respectively to deviate significantly within the light RCo₅ MAE trend. Here we focus on the anomalous behavior of NdCo₅ and SmCo₅ and find the origin of the deviation stemming from the shape of the 4f charge density.