Theoretical study of the magnetism within Gd/Mo and Gd/W multilayers

The local-spin-density approximation (LSDA) and generalized-gradient approx imation of Perdew, Burke, and Ernzerhof (PBE) are implemented within the fr amework of the semirelativistic self-consistent tight-binding linear-muffin -tin orbital in the atomic-sphere-approximation scheme. Energy-volume and m agnetovolume studies of bulk Gd, Mo, and W are presented. Use of the LSDA i n the study of Gd indicates that the antiferromagnetic structure is energet ically favorable at the equilibrium lattice parameter which is 3% smaller t han the experimental value. Application of the PBE functional predicts the experimentally observed ferromagnetic ground state at an equilibrium lattic e parameter close to (+0.5%) the experimental value. Magnetovolume studies of Mo and W predict that, although both these metals possess a nonmagnetic bcc ground state, they will exhibit antiferromagnetic behavior at large vol umes regardless of whether the structure of the idealized unit cell is bcc, fee, or hcp. Magnetic behavior as a consequence of volume expansion is als o predicted to occur on the Mo or W sites within Gd/X (X=Mo,W) bilayers. Mo reover, for the case of a 5Gd/3Mo multilayer, constructed using the volume parameters of bulk Gd, the magnetic behavior of the Gd and Mo layers is nea rly identical to that of the constituent bulk elements at the same volume. We have thus demonstrated that any possible occurrence of a magnetic moment on a Rife or W site within such a multilayer is a direct consequence of vo lume effects only.