Calculated elastic constants and electronic and magnetic properties of bcc, fcc, and hcp Cr crystals and thin films

Abstract

In order to understand the phase stability and physical properties of artificial close-packed Cr films, we have performed electronic structure and total-energy calculations for Cr in bcc, fcc, and hcp structures based density functional theory with local-density approximation plus generalized gradient corrections. The calculated lattice and elastic constants of the antiferromagnetic bcc Cr are in good agreement with experiments. The lattice constants of fcc and hcp Cr determined from the total-energy-volume curves are close to that of the reported close-packed Cr thin films. However, the calculated elastic constants show that fcc Cr is unstable against any shear deformation while hcp Cr would be unstable against only symmetry-breaking lattice distortions. Based on these findings, it is argued that the recently observed ultrathin close-packed Cr films on hcp Co form a hcp structure, and that the thin Cr films deposited on Au ͑Ir͒ ͑111͒ reported in the early 1970's are unlikely to have a fcc structure. Comparison of the calculated and experimental x-ray absorption spectra also indicates the formation of a hcp Cr phase for close-packed Cr thin films on hcp Co. Though the density-of-states at the Fermi level of fcc and hcp Cr is large, no ferromagnetic state is found for these structures. No simple commensurate antiferromagnetic state is found for the fcc and hcp Cr either. The results of the same calculations performed for the ͑111͒ fcc Cr 3 /hcp Co 6 , hcp Cr 3 /hcp Co 7 , fcc ͑hcp͒ Cr 3 /fcc Cu 6 ͑111͒ multilayers are also reported in order to see the effects of the interfaces.

Ab initiostudies of spin-spiral waves and exchange interactions in3dtransition metal atomic chains

“…1b). For comparison, we notice that in previous GGA calculations [40], the FM state could not be stabilized in bulk Cr metal, whilst the magnetization energy of the AF state is rather small (∼0.016 eV/atom).…”

Spin-density wave in Cr: Nesting versus low-lying thermal excitations

“…However, the interpretation of our results will not be affected by small deviations of U. LDA and GGA obtain the simple antiferromagnetic configuration as ground state instead of the experimental spindensity wave ground state. [7][8][9][11][12][13][14][15][16][19][20][21] Figure 1 shows that also for LDA+ U the simple antiferromagnetic configuration has the lowest energy, with an equilibrium lattice constant of 2.80 Å ͑Fig. 1͒ and a magnetic moment of 0.47 B ͑Fig.…”

“…It prompted several ab initio investigations of SDW Cr and attempts to reconcile theory and experiment. [7][8][9][10][14][15][16][17][18][19][20][21] Some time ago, a remarkable solution to the conflict was put forward by Uzdin and Demangeat 22 based on a model Hamiltonian study ͓periodic Anderson model ͑PAM͔͒. It builds further upon ideas that were in an embryonic form formulated in the work of Hafner et al 8,9 Their argument goes as follows.…”

Diffusion, surface alloy formation, and spin alignment in Fe/Cr(001) systems and superlattices

“…This material is a singular transition metal characterized by a dominant antiferromagnetic (af) bulk structure [20] and the magnetic behavior of Cr layers in superlattice or sandwich structures has been shown to be particularly complex [22 -24]. The ferromagnetic (fm) ordering in Cr ultra thin films can be induced in epitaxial (pseudomorphic) monolayer which is otherwise nonmagnetic (nm) or antiferromagnetic (af).…”