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We present a detailed analysis of the temperature dependence of the thermal conductivity of a ferroelectric PbTiO3 thin film deposited in a composition-spread geometry enabling a continuous range of compositions from ∼25% titanium deficient to ∼20% titanium rich to be studied. By fitting the experimental results to the Debye model we deconvolute and quantify the two main phonon-scattering sources in the system: ferroelectric domain walls (DWs) and point defects. Our results prove that ferroelectric DWs are the main agent limiting the thermal conductivity in this system, not only in the stoichiometric region of the thin film ([Pb]/[Ti] ≈ 1) but also when the concentration of the cation point defects is significant (up to ∼15%). Hence, DWs in ferroelectric materials are a source of phonon scattering at least as effective as point defects. Our results demonstrate the viability and effectiveness of using reconfigurable DWs to control the thermal conductivity in solid-state devices., This work received financial support from the Ministerio de Economía y Competitividad (Spain) under project nos. MAT2016-80762-R, PID2019-104150RB-100, and PGC2018-097789-B-I00, Xunta de Galicia (Centro Singular de Investigación de Galicia Accreditation 2019-2022, ED431G 2019/03), the European Union (European Regional Development Fund-ERDF), and the European Commission through the Horizon H2020 funding by H2020-MSCA-RISE-2016-Project No. 734187-SPICOLOST. E.L. is a Serra Húnter Fellow (Generalitat de Catalunya). E.L. acknowledges funding received from the European Union’s Horizon 2020 Research and Innovation Program through the Marie Skłodowska-Curie Actions: Individual Fellowship-Global Fellowship (ref. MSCA-IF-GF-708129). D.B. acknowledges financial support from MINECO (Spain) through an FPI fellowship (BES-2017-079688). The work at Cornell was supported by the Army Research Office under grant W911NF-16-1-0315. H.P. acknowledges support from the National Science Foundation [Platform for the Accelerated Realization, Analysis, and Discovery of Interface Materials (PARADIM)] under Cooperative Agreement No. DMR-1539918.

We report the disentanglement of bulk and interfacial contributions to the thermally excited magnon spin current in the spin Seebeck effect under static heating. For this purpose, we have studied the dependence of the inverse spin Hall voltage and the thermal conductivity on the magnetic layer thickness. Knowledge of these quantities allows us to take into account the influence of both sources of thermal spin current in the analysis of the voltage dependence. The magnetic layer thickness modulates the relative magnitude of the involved thermal drops for a fixed total thermal difference throughout the sample. In the end, we attain the separate contributions of both sources of thermal spin current—bulk and interfacial—and obtain the value of the thermal magnon accumulation length scale in maghemite, which we find to be 29(1) nm. According to our results, bulk magnon accumulation dominates the spin Seebeck effect in our studied range of thicknesses, but the interfacial component is by no means negligible., This work was supported by the Spanish Ministry of Science [through Project Nos. MAT2014-51982-C2-R, MAT2016-80762-R, MAT2017-82970-C2-R, and PID2019-104150RB-I00 (including FEDER funding) and the Aragón Regional government (Project No. E26)]. P.J.-C. acknowledges Spanish MECD for support through FPU program (Reference No. FPU014/02546). D.B. acknowledges support from MINECO (Spain) through an FPI program (No. BES-2017-079688). R.R. also acknowledges support from the European Commission through the Project No. 734187-SPICOLOST (H2020-MSCA-RISE-2016), the European Union's Horizon 2020 research and innovation program through the Marie Sklodowska-Curie Actions Grant Agreement SPEC No. 894006, and the Spanish Ministry of Science (No. RYC 2019-026915-I). Authors acknowledge the Advanced Microscopy Laboratory-INA University of Zaragoza for offering access to their instruments. C. L-B. acknowledges Xunta de Galicia and ESF for a PhD Grant (ED481A-2018/013).

We introduce a single-step lithography process based on Ga+-focused ion beam (FIB) irradiation to trigger a topotactic transformation on SrFeO3−δ thin films, from the perovskite to the brownmillerite (BM) crystal structure. The crystallographic transformation is triggered by preferential oxygen sputtering by Ga+-FIB irradiation, which favors the formation of the SrFeO2.5 BM phase. The transformation has been verified through micro-Raman spectroscopy on thin films subjected to Ga+-FIB irradiation under 5 kV and 30 kV. Inducing crystallographic transformations by FIB in a single-step process (without the need of resists), at a very high speed (low Ga+ doses are required, in the range of 1015 ions/cm2), with very high spatial resolution (limited by the ion beam spot, of a few square nanometers) and with potential for upscaling using broad Ga+ beams, this approach represents a significant forward step over previous methods using multistep lithographic or electrochemical procedures. All these virtues make this process appealing to develop applications based not only on SrFeO3−δ thin films but also on other oxide films harnessing topotactic transformations., This work was supported by the Spanish Ministry of Economy and Competitivity through Project Nos. MAT2017-82970-C2-2-R, MAT2018-102627-T, and MAT2016-80762-R (including FEDER funds), by the Aragon Regional Government through Project No. E13_20R (with European Social Fund), by Xunta de Galicia (Centro singular de investigación de Galicia accreditation 2016–2019, No. ED431G/09), and by the European Union (European Regional Development Fund-ERDF) and the European Commission through the Horizon H2020 funding by H2020-MSCA-RISE-2016-Project No. 734187–SPICOLOST. D.B. acknowledges financial support from Ministerio de Ciencia e Investigación (Spain) through an FPI fellowship (No. BES-2017-079688).