Theoretical and Experimental Investigation on Structural, Electronic and   Magnetic Properties of layered Mn5O8
  We have investigated the crystal, electronic, and magnetic structure of Mn5O8 by means of state of-the-art density functional theory calculations and neutron powder diffraction (NPD) measurements. This compound stabilizes in the monoclinic structure with space group C2/m where the Mn ions are in the distorted octahedral and trigonal prismatic coordination with oxygen atoms. The calculated structural parameters based on total energy calculations are found to be in excellent agreement with low temperature NPD measurements when we accounted correct magnetic structure and Coulomb correlation effect into the computation. Bond strength analysis based on crystal orbital Hamiltonian population between constituents indicating strong anisotropy in the bonding behavior which results in layered nature of its crystal structure. Using fully relativistic generalized-gradient approximation with Hubbard U (GGA+U) we found that the magnetic ordering in Mn5O8 is A-type antiferromagnetic and the direction of easy axis is [1 0 0] in agreement with susceptibility and NPD measurements. However, the calculation without the inclusion of HubbardU leads to ferrimagnetic half metal as ground state contradictory to experimental findings, indicating the presence of strong Coulomb correlation effect in this material. The GGA calculations without Coulomb correction effect itself is sufficient to reproduce our experimentally observed magnetic moments in various Mn sites. 
M. R. Ashwin Kishore, H. Okamoto, Lokanath Patra, R. Vidya, Anja O.   Sjastad, H. Fjellvag, and P. Ravindran
cond-mat.mtrl-sci