The mechanical, lattice dynamics, thermal and intrinsic magnetic properties of novel orthorhombic L10-like type FePt alloy

In this work, an orthorhombic Cmmm FePt structure with a lower energy than the experimentally known L10FePt structure is discovered based on the particle swarm optimization algorithm. The structural stability is verified by three aspects, namely formation enthalpy, mechanical stability and lattice dynamic stability. The fundamental physical properties of the newly discovered structure are calculated, and a comparison with L10FePt is performed due to the fact that the Cmmm structure can be regard as a slightly distorted L10 structure. The elastic and lattice dynamics properties of the Cmmm structure are almost comparable to those of the L10 structure. The coefficients of thermal expansion of the Cmmm structure is slightly lower. The intrinsic magnetic properties of the Cmmm structure are better than those of the L10 structure, except for the nearly identical magnetocrystalline anisotropy. Therefore, the orthorhombic Cmmm structure could also be suitable for permanent magnets and magnetic storage mediums. Finally, the critical pressures of ferromagnetism collapse are calculated, and the critical pressure of the Cmmm structure is nearly 20 GPa higher than that of the L10 structure.