Quantum Paraelectric Glass State in SrCu3Ti4O12

Magnetic and dielectric studies of SrCu3Ti4O12 carried out over 5-300K confirm antiferromagnetic (AFM) ordering of Cu-spins at TN =23K. Dielectric constant {\epsilon}' measured across 1Hz-1MHz signifies quantum paraelectric character, Barrett-fittable almost down to TN. Competition of athermal fluctuations and the literature-reported magneto-phonon-softening near TN manifests a maiden quantum paraelectric glass (QPG) state. Emergent AFM-field tunes the otherwise quantum ordering (at absolute-zero) of the dipoles to finite-temperature kinetic glass transition; spectral dispersion of dielectric constant unambiguously manifested and characterized. Vogel-Fulcher glass-kinetics parameterization sets the almost relaxation-free QPG state in SrCu3Ti4O12 apart from an emergent scaling-class, to which typical ferroelectric relaxors belong.