  The predicted physical properties of double perovskites have usually been
compromised by their intrinsic B-antisite (AS) disorder effect, but the
relationship between them is still unclear for the La2MnCoO6 (LMCO) system.
This study focuses on controlling the AS disorder and quantitatively reveals
correlations with magnetic and electronic states in epitaxial LMCO films grown
on (111) SrTiO3 substrates. The AS fraction was precisely controlled by tuning
the growth conditions as evaluated from saturation magnetization and x-ray
reflection profiles. The saturation magnetization at 5 K decreased linearly
from 6 uB per formula unit by 50% as the AS fraction increased from 0
(perfectly ordered) to 0.5 (fully disordered). The x-ray absorption
spectroscopy revealed that valence states of Mn and Co were 4+ (3d^3) and 2+
(3d^7), respectively, regardless of AS fraction. A local-spin-moment model is
proposed to explain the net magnetizations with and without AS disorder and
Mn/Co valence states, suggesting that only the rearrangement of local spin
moment of Co at the antisite plays a key role in tuning the magnetism in this
LMCO system.
