Magnetic field induced critical dynamics in magnetoelectric TbPO4

We report on the magnetoelectric dynamics in the linear magnetoelectric antiferromagnet TbPO₄ studied by broadband dielectric spectroscopy. For the phase transition into the magnetoelectric antiferromagnetic phase at TN≈2.30.28em0exK, a finite magnetic field H induces critical behavior in the quasistatic permittivity ε^'(T). Plotting the corresponding anomaly as a function of T/TN(H), we observe the scaling behavior Δε^'∝H², a clear fingerprint of linear magnetoelectric antiferromagnets. Above the phase transition, we find a critical slowing down of the ferroic fluctuations in finite magnetic field. This behavior can be understood via a magnetic field induced relaxational response that resembles the soft-mode behavior in canonical ferroelectrics and multiferroics.