  The microscopic origin of the high Neel temperature (T_N) observed
experimentally in SrTcO_3 has been examined using a combination of ab-initio
electronic structure calculations and mean-field solutions of a multiband
Hubbard model. The G-type antiferromagnetic state is found to be robust for a
large region of parameter space, with large stabilization energies found,
surprisingly, for small values of intraatomic exchange interaction strength as
well as large bandwidths. The microscopic origin of this is traced to specific
aspects associated with the d3 configuration at the transition-metal site.
Considering values of interaction strengths appropriate for SrTcO3 and the
corresponding 3d oxide SrMnO_3, we find a ratio of 4:1 for the TN as well as
magnitudes consistent with experiment.
