  Materials based on the Sm-Co system exhibit remarkable magnetic performance
due to their high Curie temperature, large saturation magnetization, and strong
magnetic anisotropy, which are the result of the electronic structure in Co and
Sm and their arrangement in the hexagonal lattice. In this paper we show, using
first-principles calculations, mean-field theory, and atomistic Monte Carlo
simulations that slight modifications of the SmCo5 crystal structure, induced
by strain or partial substitution of Sm by Ce, change the exchange interaction
energy and increase the magnetocrystalline anisotropy energy drastically. This
finding shows how small changes in local-structure environments lead to
substantial changes in macroscopic properties and enables the optimization of
high-performance materials at the atomic level.
