Title: Magnetic ground state of SrRuO$_3$ thin film and applicability of standard first-principles approximations to metallic magnetism,
Abstract: A systematic first-principles study has been performed to understand the
magnetism of thin film SrRuO$_3$ which lots of research efforts have been
devoted to but no clear consensus has been reached about its ground state
properties. The relative t$_{2g}$ level difference, lattice distortion as well
as the layer thickness play together in determining the spin order. In
particular, it is important to understand the difference between two standard
approximations, namely LDA and GGA, in describing this metallic magnetism.
Landau free energy analysis and the magnetization-energy-ratio plot clearly
show the different tendency of favoring the magnetic moment formation, and it
is magnified when applied to the thin film limit where the experimental
information is severely limited. As a result, LDA gives a qualitatively
different prediction from GGA in the experimentally relevant region of strain
whereas both approximations give reasonable results for the bulk phase. We
discuss the origin of this difference and the applicability of standard methods
to the correlated oxide and the metallic magnetic systems.