  From the spin polarized density functional total energy calculations, we
shown that the ground state of cubic perovskite RbMnF$_3$ is an
antiferromagnetic (AFM) insulator due to the super-exchange mechanism, in
agreement with the other theoretical and experimental results. After tetragonal
distortion along the c-axis, keeping the predicted volume, our results
indicated that the strain-induced magnetic phase transition from an AFM
insulator to a half metallic ferromagnetic (HM-FM) state is available by the
tetragonal distortion due to the insulator -- half metallic transition. The
predicted electronic and magnetic properties of strain-induced RbMnF$_3$ show
the HM-FM nature, making strain-induced RbMnF$_3$ suitable for spintronic
application.
