Dynamic magnetoelectric effect and phase diagram of the polar magnet Ni 2 MnTeO 6

The polar magnet ${\mathrm{Ni}}₃{\mathrm{TeO}}₆$ is known for its large magnetoelectric (ME) effect at cryogenic temperatures ($\ensuremath{\sim}52$ K) and in high magnetic fields ($\ensuremath{\sim}9$ T). Substitution of Ni with Mn could be an effective way to enhance magnetic ordering temperature and reduce critical magnetic fields. In this work, we have investigated the anisotropic ME effect in Mn-substituted polar magnet ${\mathrm{Ni}}₂\mathrm{MnTe}{\mathrm{O}}₆$ through measurements of the temperature and magnetic field dependence of the dynamic ME coefficient (${\ensuremath{\alpha}}_{\mathrm{E}}=\mathrm{d}E/\mathrm{d}H)$ and the dielectric permittivity (${\ensuremath{\varepsilon}}_{\mathrm{r}}$) on a single-crystal sample. It is found that ${\ensuremath{\alpha}}_{\mathrm{E}}$ exhibits pronounced peaks/dips whenever a magnetic phase transition is induced by either temperature or magnetic field. The maximum dynamic ME effect occurs at 45 K in $H\ensuremath{\sim}3.95$ T and at 68 K in $H\ensuremath{\sim}3.4$ T for $H//c$ axis and $ab$ plane, respectively. The obtained phase diagrams illustrate distinct regimes with dominant ME effect at phase boundaries. Our study demonstrates that a significant dynamic ME effect comparable to multiferroic composites can be expected in single-phase polar magnets. Moreover, it is proposed that the dynamic ME coefficient ${\ensuremath{\alpha}}_{\mathrm{E}}$ could act as a sensitive probe to detect subtle phase transitions in insulating magnets.