Evidence of the impurity spin coupling with quantum paraelectric fluctuations in CaTi1-xRuxO3

TL;DR

This study provides experimental evidence that impurity spins in CaTi1-xRuxO3 couple with quantum paraelectric fluctuations, leading to a ferromagnetic-like transition even at low impurity concentrations.

Contribution

It reveals the coupling between magnetic impurity spins and quantum paraelectric fluctuations in CaTi1-xRuxO3, a phenomenon not previously demonstrated.

Findings

Impurity doping induces ferromagnetic-like transition.

Coupling between Ru spins and quantum fluctuations observed.

Spin-polarized ground state confirmed in CaTi1-xRuxO3.

Abstract

Quantum paraelectrics are materials in which a long-range ferroelectric/antiferroelectric order is suppressed by quantum fluctuations, i.e. zero-point motion of the lattice prevents condensation of the soft polar phonon mode even at T = 0 K. The most prominent quantum paraelectric materials are SrTiO3, KTaO3, and CaTiO3. Here we focus on peculiar properties of the pseudo-cubic perovskite CaTi1-xRuxO3 system. Namely, as soon as any concentration of either Ru or Ti is introduced into the pure compounds, a concentration-independent ferromagnetic-like transition occurs at low temperatures. We present the experimental evidence of the spin-polarized ground state of CaTi1-xRuxO3 induced by coupling of magnetic moments of Ru impurities with quantum paraelectric fluctuations in the host compound CaTiO3.