  The $4d$ and $5d$ transition metal oxides have become important members of
the emerging quantum materials family due to competition between onsite Coulomb
repulsion ($U$) and spin-orbit coupling (SOC). Specifically, the systems with
$d^5$ electronic configuration in an octahedral environment are found to be
capable of posessing invariant semimetallic state and perturbations can lead to
diverse magnetic phases. In this work, by formulating a multi-band Hubbard
model and performing SOC tunable DFT+$U$ calculations on a prototype SrIrO$_3$
and extending the analysis to other iso-structural and isovalent compounds, we
present eight possible electronic and magnetic configurations in the $U$-SOC
phase diagram that can be observed in the family of low-spin $d^5$ perovskites.
They include the protected Dirac semimetal state, metal and insulator regimes,
collinear and noncollinear spin ordering. The latter is explained through
connecting hopping interactions to the rotation and tilting of the octahedra as
observed in GdFeO$_3$. Presence of several soft phase boundaries makes the
family of $d^5$ perovskites an ideal platform to study electronic and magnetic
phase transitions under external stimuli.
