  M-type hexaferrite BaFe12O19 was recently reported to be a new type of
quantum paraelectrics with triangular lattice by showing a low temperature
dielectric plateau due to quantum fluctuation. It has also been proposed to
have a possible quantum-dipole liquid ground state. To suppress its quantum
fluctuations and reach a possible quantum critical point, we have tuned its
quantum paraelectricity in three ways: (i) 57Fe isotope replacement; (ii)
in-plane compressive strain; and (iii) hydrostatic pressure. It is found that
95% 57Fe replacement and the in-plane strain are more effective to drive its
ground state closer to a critical region by inducing a peak feature in the
temperature dependence of dielectric constant. In contrast, the application of
hydrostatic pressure pushed the system away from the quantum critical point by
gradually suppressing the plateau feature in dielectric constant. Our combined
efforts reveal the potential of the M-type hexaferrites for studying the
quantum critical behaviors.
