Comments are made on total energy band calculations as tools for exploring properties of solids; the importance of fixed spin moment calculations is noted. Use of energy — magnetisation curves to locate magnetic phases is described. Detailed results for fcc and bcc Co and Ni and phase diagrams on the magnetisation — volume plane exhibit two new phases for each metal and show that ferromagnetic fcc Co and bcc Ni break down at small volumes and make first order transitions to nonmagnetic phases in a metamagnetic volume range.

First-principles total-energy calculations on tetragonal Fe show that the ferromagnetic and antiferromagnetic phases have tetragonal equilibrium states with c/a.1, the fcc value. The bulk layers of an epitaxial film of Fe on Cu~001!, which are almost fcc with the Cu lattice constant, are shown to be stable in the antiferromagnetic phase, but inherently unstable in the ferromagnetic phase. The structure of tetragonal equilibrium antiferromagnetic Fe is estimated to be a53.47 A, c53.75 A. @S0163-1829~99!04125-9#

The energy bands and magnetic moments of the magnetic phases of face-centred-cubic iron are calculated from first principles with the augmented spherical wave method and the fixed-spin-moment procedure. An antiferromagnetic phase that requires a four-atom cell to exist is added. This phase is the current ground state of the bulk layers of Fe film epitaxial on Cu(001). A ferrimagnetic phase and a very-low-spin phase are also found and compared with previous work. In a narrow range of volume that includes the bulk layers of the Fe films on Cu(001) at least eight magnetic phases exist.

The occurrence of magnetic phases in FeCr and FeCo in the CsCl structure has been studied by first-principles total-energy calculations with a sensitive and accurate method, using a four-atom unit cell. When both atoms in such binary compounds can be strongly magnetic, unusual structures are found. These materials have ferromagnetic (FM) and antiferromagnetic (AF) phases, but the equilibrium state for both is FM. However at 3% expansion of the lattice constant the ground state of FeCr becomes AF, whereas in FeCo the AF phase is never the ground state. The AF phase in both FeCr and FeCo has an unusual structure in that both the Fe and the Cr or Co sublattices are separately AF. In both the FM and AF phases at the equilibrium volume, the Fe moment is reduced in FeCr, but enhanced in FeCo from that in pure body-centered-cubic (bcc) Fe; also the Cr moment is increased from that in pure bcc Cr, while the Co moment is similar to the moment in hexagonal-dose-packed Co. In the FM phase of FeCr, but not in FeCo, the two Fe atoms in the four-atom unit cell have different moments, which have opposite signs at large volume.

The magnetic phase structure of FeCr in the CsCl (B-2) structure is studied as a function of volume by first-principles calculations using a four-atom unit cell. The ground state is found to be ferromagnetic (FM), but at a 3% expansion of the lattice constant the ground state becomes type-I antiferromagnetic (AF). The AF phase has the unusual structure in that both Fe and Cr sublattices are separately type-I AF. In both the FM and AF phases the Fe moment is reduced from that in pure bcc Fe and the Cr moment increased from that in pure bce Cr. [S0163-1829(98)02630-7].

It is shown that two special properties of Cr are needed to explain its antiferromagnetism. One special property is the well known sensitivity to antiferromagnetic spin-density waves due to nesting of the Fermi surface. A second new special property comes from first-principles total-energy calculations on bcc Cr, which show that, although-the lowest energy state is nonmagnetic, a small expansion of the lattice brings a second-order transition into a type-I antiferromagnetic phase with rapidly rising local moments. The combined properties provide a mechanism for stabilization of the unusual antiferromagnetic ground state, since a spin-density wave which modulates the moments of the antiferromagnetic phase can be used to compensate the strain energy of the lattice expansion. This combined mechanism also explains various properties of Cr,such as the great sensitivity of the antiferromagnetism to pressure, that are otherwise puzzling.

Previous first-principles calculations on the magnetic phases of nine FeX and Fe(2)XY compounds in the CsCl structure, where X and Y are 4d elements from Tc to Ag, are extended to include type-II as well as type-I antiferromagnetism. The antiferromagnetism of FeRh and Fe2RuRh is greatly enhanced in the type-Il phase and FeRu in the type-II phase becomes the fifth such compound with an antiferromagnetic ground state. However in the weaker antiferromagnets FePd and Fe2RhPd the equilibrium state of the type-II phase has a higher energy than the type-I phase.

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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, Fe2RhPd, Fe2RuRh, and FeRh; Fe2RuRh 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 mu(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 mu(B)) in the ferromagnetic phase.

bcc and fcc elements 3d transition-metal alloys (CsCl) 3d transition-metal alloys (CuAu) 3d transition-metal alloys (Cu3Au) 3d transition-metal alloys (AuCu3) 4d transition-metal alloys (CsCl) 4d transition-metal alloys (CuAu) 4d transition-metal alloys (Cu3Au) 4d transition-metal alloys (AuCu3) description of results.

We have used photoemission measurements of the Fe-3s core level to investigate the Fe local moments in two Fe-Ni alloys containing 70% and 72.5% Fe in both the γ- and α-phases. Previous magnetization measurements indicate that in this composition range the average total moments of alloys in the γ-phase are considerably lower than in the α-phase. However, our photoemission measurements suggest that the local moment on the Fe site is approximately the same in both phases. Furthermore, a determination of the spin-splitting suggests that at room temperature the Fe local moments in the alloys are smaller than in pure Fe.

The magnetic structures of the ordered transition-metal compounds FePd and FeRh are found in both the CsCl and CuAu atomic structures by first-principles total-energy calculations. The ground state of FePd is shown to be the CuAu structure and ferromagnetic, in agreement with experiment. However, at equilibrium in the CsCl structure, where FePd is metastable, FePd behaves just like FeRh and has an antiferromagnetic ground state. A ferromagnetic phase of FePd lies 0.5 mRy higher in energy at the equilibrium volume and, like FeRh, but more readily, undergoes a first-order phase transition from the antiferromagnetic phase to the ferromagnetic phase at an expanded lattice constant or in a magnetic field

The magnetic structures of the ordered transition-metal compounds FePd and FeRh are found in both the CsCl and CuAu atomic structures by first-principles total-energy calculations. The ground state of FePd is shown to be the CuAu structure and ferromagnetic, in agreement with experiment. However, at equilibrium in the CsCl structure, where FePd is metastable, FePd behaves just like FeRh and has an antiferromagnetic ground state. A ferromagnetic phase of FePd lies 0.5 mRy higher in energyat the equilibrium volume and, like FeRh, but more readily, undergoes a first-order phase transition from the antiferromagnetic phase to the ferromagnetic phase at an expanded lattice constant or in a magnetic field.

We show that bulk moduli, determined from first-principles total-energy electronic calculations using the local-spin-density and atomic-sphere approximations in cubic structures, are in remarkable agreement with experiment for all of the nonmagnetic, ferromagnetic, and antiferromagnetic 3d and 4d transition and noble metals. Good agreement with experiment is achieved without relativistic corrections which, by themselves, introduce sizable errors in calculated bulk moduli.

First-principles augmented-spherical-wave fixed-spin-moment solutions of the Kohn-Sham band equations are used to study the volume dependence of the total energy and the local moments in ordered FeAl and FeV. The solutions yield volume ranges with stable ferromagnetic and metastable type-I antiferromagnetic states for both FeAl and FeV, with energy differences less than congruent-to 0.5 mRy over a wide range of volumes around equilibrium. For FeV, an unstable mixed antiferromagnetic state with equal and opposite iron and vanadium local moments is also found. Solutions corresponding to type-II antiferromagnetism were not found. Near equilibrium iron local moments are congruent-to 0.5 mu(B) for the antiferromagnetic state, and congruent-to 0.7 muB for the ferromagnetic state for FeAl, and congruent-to 0.7 mu(B) for both the ferromagnetic and antiferromagnetic states in FeV. The calculated lattice constant at equilibrium is within 1.8% of the experimental value for FeAl, and within 1.4% for FeV.