IMF2017

The term ‘ferroic glass’ was coined [Ren, 2014] for strain, magnetic, and electric dipolar nanodomain states, which undergo glassy dynamic criticality as T --> T_g and non-ergodicity at T < T_g. While these features are also found in ‘superdipolar glass’ systems of matrix isolated magnetic nanoparticles as in [Co₈₀Fe₂₀(0.9 nm)/Al₂O₃(3 nm)]₁₀ multilayers [Bedanta, Petracic, Kleemann, 2015], the mesoscopic ‘ferroic glasses’ are generally more complex due to the much closer relationship of the nanodomains to the embedding matrix. This is shown for the archetypical relaxor PbMg_1/3Nb_2/3O₃ [Kleemann, Dec, 2016], where quenched electric random fields give rise to creation and growth of polar nanoregions (PNR) on cooling toward T_g with a spectrum of relaxation frequencies skewing from Lacroix-Béné to Cole-Davidson-type. It becomes replaced by relaxation and creep-like domain wall dynamics below T_g ~ 240 K, where the PNR percolate [Jeong et al., 2005; Koreeda et al., 2013] and form a ferroelectric microdomain state under the control of the ferroelectric F_1u soft lattice mode [Fu et al., 2012].