First-principles total-energy calculations that constrain the total moment in each cell while iterating to self-consistency are applied systematically to FeX compounds in the CsCl structure; X ranges over the 4d elements from Tc to Ag, including pairs of elements of adjacent atomic number in a four-atom cell. The equilibrium energies of the ferromagnetic and type-I antiferromagnetic phases are calculated. The energy of the equilibrium antiferromagnetic state with respect to the equilibrium ferromagnetic state is shown to oscillate with change of electron number and to be negative, hence favoring antiferromagnetism, for FePd, ${\mathrm{Fe}}_2$RhPd, ${\mathrm{Fe}}_2$RuRh, and FeRh; ${\mathrm{Fe}}_2$RuRh is by far the most strongly favored antiferromagnet of these compounds. The trends of lattice constants, bulk moduli, and magnetic moments are found; the largest Fe moments (more than 3${\mathrm{\mu }}_{\mathit{B}}$) occur in FeRh in both the ferromagnetic and antiferromagnetic phases; the X moments vanish in the antiferromagnetic phase, but have finite values (up to 1${\mathrm{\mu }}_{\mathit{B}}$) in the ferromagnetic phase.

• Received 3 February 1995

DOI:https://doi.org/10.1103/PhysRevB.52.3448