Dynamic multiferroicity of a ferroelectric quantum critical point*

Dynamical multiferroicity, where fluctuations of electric dipoles lead to magnetisation, is an example of where two coexisting orders are impossible to disentangle [1]. We calculate the magnetic susceptibility near the ferroelectric quantum critical point (FE QCP) and find a region with enhanced magnetic signatures that appears near the FE QCP, and is controlled by the tuning parameter of the ferroelectric phase. We thus suggest that any ferroelectric quantum critical point may be an inherent multiferroic quantum critical point. The effect is small but observable, and we suggest the quantum paraelectric strontium titanate as a candidate material where the magnitude of the induced magnetic moments can be ~5 x 10⁷ µ_B per unit cell
near the FE QCP [2].

[1] D. M. Juraschek et al., PhysRevMat.1.014401 (2017).
[2] K. Dunnett et al., arXiv:1808.05509 (2018).