Quantum paraelectricity to dipolar glass transition in Sc doped BaFe12O19 single crystals

We report a quantum paraelectric (QP) to dipolar glass (DG) phase transition induced by Sc substitution in ferrimagnetic hexaferrite BaFe12−xScxO19 (0≤x≤2.4) single crystals. The DG behavior is revealed via anisotropic dielectric spectroscopy, polarization, and specific heat measurements. The phase evolution from QP to DG (0.5≤x≤1.2) and finally to the nonpolar state (x≥ 2.4) with increasing x is found to be due to the competition between the enhanced polar instability by lattice volume expansion and disordered/frustrated dipole-dipole interaction induced by the partial replacement of Sc3+ for Fe3+ in the bipyramids. Our results suggest further experimental clues to realize possible multiferroicity with strong displacive ferroelectricity in BaFe12O19 and other magnetic materials.