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Title: Stanislav Kamba: Making EuO multiferroic by epitaxial strain engineering
Number: 60/21
Status: Closing date exceeded
Begin: Wednesday, 01.12. 2021, 14:10
Tutor: Ross H. Colman
Location: Online on zoom https://cesnet.zoom.us/j/95804267376


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We have a pleasure to invite you to attend the joint seminar

of the Department of Condensed Matter Physics (DCMP)
and the Materials Growth and Measurement Laboratory (MGML) http://mgml.eu.

Program

Making EuO multiferroic by epitaxial strain engineering

lecture given by:

Stanislav Kamba

Institute of Physics of the Czech Academy of Sciences, Prague, Czech Republic

on Wednesday, 1.12. 2021 from 14:10
Online via zoom:https://cesnet.zoom.us/j/95804267376
password is on question via email: This e-mail address is being protected from spambots. You need JavaScript enabled to view it

Ross H. Colman
On behalf of the DCMP and MGML


Abstract

Infrared spectroscopy is effective tool for the study of polar soft phonons driving the displacive ferroelectric phase transitions because it can reveal the phase transitions without any structural investigations or without any electrodes required for dielectric measurements.
We will demonstrate application of infrared spectroscopy for already published studies of strain-induced ferroelectric phase transition in SrTiO3 and EuTiO3 [1] and newly for investigation of strained EuO ferromagnet.[2]
Our first-principles density functional calculations using a hybrid functional predicted strain-induced ferroelectric phase transition in ferromagnetic EuO with a tensile strain superior to 5%. For that reason, we investigated different EuO films grown using molecular beam epitaxy on various substrates inducing strain from 0 to 6.4 %. To achieve strain higher than 5 %, we had to prepare and characterize (EuO)2/(BaO)2 superlattices on (001) LSAT substrates. In this case the EuO and BaO are nominally strained by +6.4 % and -1.2 %, respectively. We found that the EuO optical phonon is drastically shifted down in comparison with the phonon in unstrained EuO and exhibits softening towards 100 K and a hardening below this temperature. This is a typical phonon behavior near ferroelectric phase transition. The system remains ferromagnetic, i.e. the superlattice becomes multiferroic at low temperatures below 30 K.

1. S. Kamba. APL Materials 9, 020704 (2021).
2. V. Goian, R. Held, E. Bousquet, Y. Yuan, A. Melville, H. Zhou, V. Gopalan, P. Ghosez, N. A. Spaldin, D. G. Schlom, and S. Kamba, Commun. Mat.1, 74 (2020).