This title appears in the Scientific Report : 2019 

Topotactic transition mechanisms in SrCoO$_{2.5+x}$ films
Schöffmann, Patrick (Corresponding author)
Pütter, Sabine / Sarkar, Anirban / Zhernenkov, Kirill / Syed Mohd, Amir / Waschk, Markus / Bhatnagar, Tanvi / Zakalek, Paul / Brückel, Thomas
Streumethoden; PGI-4
Physik Nanoskaliger Systeme; ER-C-1
Streumethoden; JCNS-2
5th International School of Oxide Electronic, Cargese (France), 2019-06-25 - 2019-07-05
Jülich Centre for Neutron Research (JCNS)
Quantum Condensed Matter: Magnetism, Superconductivity
Controlling Collective States
Transition metal oxides are a big research topic, because they offer a wide range of possible applications, particularly in information and energy technology. One such system is strontium cobaltite (SrCoO2.5+x), which exists in two distinct topotactic phases, depending on the oxygen content. SrCoO3 is a ferromagnetically ordered metal with a Curie temperature of 305 K, but the system becomes an antiferromagnetic insulator with a Néel temperature of 570 K, when the oxygen content is decreased to SrCoO2.5. Along with this magnetic transition, the structure changes from perovskite to the orthorhombic brownmillerite, with the missing oxygen atoms forming vacancy channels [1]. Because of the multivalent Co states and high oxygen mobility it is a promising material for device applications [2]. To control the oxygen content, several possibilities exist. We focus on annealing in oxidising conditions and applying variable strain with a piezoelectric substrate to the film.We grow thin films of SrCoO2.5 by molecular beam epitaxy on SrTiO3 and LSAT substrates for investigations of oxygen annealing induced transitions and 0.7(Pb(Mg1/3Nb2/3)O3)-0.3(PbTiO3) (PMN-PT), a piezoelectric substrate, to study the possibility of a strain dependent oxidation state.To be able to successfully control the oxidation state and transfer strain from the substrate to the film, a high sample quality and epitaxy is mandatory. Thus, we present the results of the film growth and quality, as well as first results of the magnetic characterisation by SQUID and neutron reflectometry for annealed and strained samples.[1] C.K. Xie et al., Appl. Phys. Lett. 99, 2011 [2] H. Jeen et al., Nature Materials 12, 2013