Based on ab initio Monte Carlo approach, finite-temperature magnetism of tetragonal Fe is studied. It is shown that the ground state magnetic structure changes from ferromagnetic to antiferromagnetic as the structure transforms from bcc to fcc. The Curie temperature or Néel temperatures are very sensitive to the lattice distortion, which decreases from bcc to fcc and then increases over the fcc range. There are a maximum of at the bcc and a minimum of around the fcc limit due to the change of the coupling distance and symmetry consideration.
REFERENCES
The total exchange energy can be described with .
Here, the exchange parameter is insensitive to the small change in volume. For example, the with bcc structure are estimated to be 14.56 and as the volume changing from , respectively.
