PMN: a minimal induced-moment soft pseudo-spin glass perspective

An argument that relaxor ferroelectricity in the isovalent alloy $\mathrm {Ba(Zr}{1-x}$\mathrm{T}\mathrm{i}${x})$\mathrm{O}$_3$ can be understood as an induced moment soft pseudo-spin glass on the B-ions of the ${\mathrm{A}\mathrm{B}\mathrm{O}}_3$ matrix is extended to the experimentally paradigmic but theoretically more complex heterovalent relaxor ${\mathrm{P}\mathrm{b}(\mathrm{M}\mathrm{g}}_{1\mathrm{/}3}{\mathrm{N}\mathrm{b}}_{2\mathrm{/}3}{)\mathrm{O}}_3$ (PMN). It is argued that interesting behaviour of the onset of non-ergodicity, frequency-dependent susceptibility peaks and precursor nanodomains can be understood from analagous considerations of the B-ions, with the displacements of the Pb ions a largely independent, but distracting, side-feature. This contrasts with conventional conceptualizations.