  Metamagnetism in antiferromagnets exhibits distinct critical behaviors and
dynamics when invoking spin reversal and rotation. Here we show a 0.05%
anisotropic strain suffices to in-situ modulate the metamagnetic critical field
of the Mott insulator Sr2IrO4 by over 50%, enabling electrical switching of the
transition. Resonant x-ray scattering and model simulation reveal that the
transition is completely tuned from the spin-flop to spin-flip type as the
strain introduces C4-symmetry-breaking magnetic anisotropy. Simultaneous
transport study indicates the metamagnetic responses are reflected in the large
elasto- and magnetoconductance, highlighting the active charge degree of
freedom in the spin-orbit-coupled Mott state and its potential for
spin-electronics.
