Lattice and polarizability mediated spin activity in EuTiO₃

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EuTiO₃ is shown to exhibit novel strong spin-charge-lattice coupling deep in the paramagnetic phase. Its existence is evidenced by an, until now, unknown response of the paramagnetic susceptibility at temperatures exceeding the structural phase transition temperature Tₛ = 282K. The "extra" features in the susceptibility follow the rotational soft zone boundary mode temperature dependence above and below Tₛ. The theoretical modeling consistently reproduces this behavior and provides reasoning for the stabilization of the soft optic mode other than quantum fluctuations.