Evidence on the quantum critical point in EuTiO3–SrTiO3 solid solution

Highlights: • Solid solution of EuTiO3-SrTiO3 samples were synthesized by solid state reaction. • X-ray diffraction reveals tetragonal distortion for Eu rich samples. • Coexistence of Eu2+ and Eu3+ was confirmed by XPS measurements. • The Neel temperature and magnetodielectric effect decreases with increase in Sr content. • Interestingly the magnetic phase diagram reveals a quantum critical point with compositional variation. EuTiO₃ (ETO) and SrTiO₃ (STO) are the two well-known analogous quantum paralelectric materials. In the present study, we synthesized Eu_1-xSr_xTiO₃ for various values of x (0 < x < 1) by solid state reaction method. X-ray diffraction (XRD) measurement performed on the synthesized samples confirmed the cubic structure with tetragonal distortion for Eu rich samples. The phase purity of the synthesized samples was also confirmed by the X-ray measurements. X-ray photoelectron spectra were measured to show that the valence state of Eu is in 2+ states. The dielectric and magnetic properties of Eu_1-xSr_xTiO₃ samples were systematically studied. The dielectric constant against temperature for pure ETO shows sudden drop at Neel temperature 5.3 K confirming the coupling between electric and magnetic polarization. The magnetization value remains constant below the Neel temperature for ETO and Eu_0.8Sr_0.2TiO₃ samples while others show paramagnetic behavior. The magneto dielectric effect shows a huge value of around 5% at 2 K for ETO and abruptly drops by Sr doping. The proposed phase diagram with the magnetic and dielectric data of Eu_1-xSr_xTiO₃ suggests a quantum critical point around the composition of Eu_0.7Sr_0.3TiO₃.