  The ferrimagnetic spinel Mn3O4 exhibits large and anisotropic changes in
electronic and structural properties in response to an applied magnetic field.
These changes are thought to result from the field-dependent tuning---via
strong spin-lattice coupling---between two nearly degenerate magnetostructural
phases. Recent variable-magnetic-field studies of Mn3O4 have been performed on
melt-grown crystals, which can exhibit twin domains due to a Jahn-Teller
structural transition below the melting temperature. Because of the near
degeneracy of the magnetostructural phases, however, strain associated with the
twin domains likely affects the magnetic responses of Mn3O4. In this report, we
present a variable-magnetic-field Raman scattering study of untwinned Mn3O4
crystals grown out of a flux below the Jahn-Teller structural transition. We
measure distinct q = 0 magnetic and vibrational excitation spectra for each
isolated magnetostructural phase of untwinned Mn3O4 crystals and determine the
symmetries of the observed excitations. We determine how the magnetostructural
phase mixture changes in response to magnetic fields applied in the magnetic
easy plane. Lastly, by comparing results on flux- and melt-grown Mn3O4
crystals, we show that the intrinsic mixture of the two magnetostructural
phases is indeed strongly influenced by the presence of twin domains.
