Silné filmy Fe2O3 a Fe3O4 připravené metodou depoyice z kapalné fáze

Microstructure, surface morphology, and magnetic properties of the films have been also investigated using SEM, AFM, and SQUID, respectively

Characterization of W-type hexaferrite thin films prepared by chemical solution deposition

Thin films of W-type hexaferrite were grown on SrTiO3(111) single crystals using the chemical solution deposition method and metalorganic precursor solutions prepared using the modified Pechini method. The synthesis of single-phase materials required optimizing the initial stoichiometry and crystallization conditions. The results showed that a concurrent excess of alkaline earth metal and deficiency in divalent metal ion (Zn2+, Co2+) favors the synthesis of pure W hexaferrites. This off-stoichiometry suppressed the formation of an exceedingly stable spinel phase at pyrolysis temperatures. The epitaxial nature of thin films, expressed as the orientation relation (00l)W || (111)SrTiO3 and [110] W || [112] SrTiO3 and hence the pronounced anisotropy of their magnetic properties as well were established by three dimensional x-ray diffraction texture analysis and magnetization measurements, respectively and enabled to identify the temperature interval in which the characteristic spin reorientation transition occurs for a specific degree of cobalt substitution.This work was supported by the Czech Science Foundation, Grant No. 19-06433S, by the Research Infrastructure NanoEnviCz (Ministry of Education, Youth and Sports of the Czech Republic, Projects No. LM2018124), by the “NanoCent” Project No. CZ.02.1.01/0.0/0.0/15_003/0000485, ERDF. Authors also acknowledge financial support of H2020-MSCA-RISE-2016 SPICOLOST Grant No. 734187 (TEM analysis, at LMA-INA, University of Zaragoza).Peer reviewe

Observation of anomalously large magnetoelectric coupling in the hexagonal Z-type ferrite films

Although the bulk hexaferrites are known to exhibit strong magnetoelectric (ME) effects near room temperature, the same effects are not realized in a thin film form. Herein, the growth of nearly epitaxial Co2Z-type hexaferrite Ba0.3Sr2.7Co2Fe24O41 (BSCFO) thin films on a SrTiO3 (111) substrate by a chemical solution deposition method is reported. The reciprocal space mapping on the annealed BSCFO films reveals broadening along the qx directions in the (0014) and (0018) peaks, indicating that the oxygen planes belonging to the off-centered octahedra have randomly distributed out-of-plane tilt to indicate significant disorder in the crystallographic orientation. Quantitative investigations reveal that both ME susceptibility and modulated electric polarization (ΔP) by magnetic field up to 370 K in the BSCFO films are always larger than those of the Co2Z-type single crystal by ≈2–15 times and further increase upon having enhanced qx broadening in the (0014) and (0018) peaks. As the off-centered octahedral sites can be a primary source of ΔP as predicted by the p–d hybridization mechanism, these results indicate that effective off-centering could be further enhanced by the orientational disorder. This study identifies the potential of applying the ME hexaferrite films for multifunctional devices.This work was financially supported by the National Research Foundation of S. Korea through 2019R1A2C2090648, 2019M3E4A1080227, and by the Ministry of Education of S. Korea through 2021R1A6C101B418. The works in Czech were supported by the GACR (Czech Science Foundation) Project Nos. 19-06433S and H2020-MSCA-RISE-2016 SPICOLOST under Grant No. 734187 for TEM analysis at LMA-INA, University of Zaragoza, and by the Nanomaterial Center for Advanced Applications(NANOCENT), No. CZ.02.1.01/0.0/0.0/15_003/0000485.Peer reviewe

Properties of BaTiO3 confined in nanoporous Vycor and artificial opal silica

Using the sol-gel technique, BaTiO3 was embedded into nanoporous Vycor and artificial vitreous opal silica for the first time. About 50 vol% of the pores was filled. In case of the Vycor glass (pore diameter 4–6 nm) only amorphous phase was revealed by XRD, IR reflectivity and Raman spectra. After additional gradual annealing, no crystallization was achieved. Chemical reaction with the SiO2 skeleton started at ~1000 K. The room-temperature IR and Raman spectra clearly show characteristic vibrational modes of the ferroelectrically distorted TiO6 octahedra without any long-range order. In case of the opal matrix (densely packed silica spheres, pore diameter up to ~50 nm), crystallization of the ferroelectric BaTiO3 appeared in coexistence with the amorphous phase, but the penetration depth of the crystalline BaTiO3 was limited. From the apparent temperature independence of the effective wide-frequency dielectric response due to the essentially temperature independent effective soft mode stiffened to ~100 cm-1, we can deduce that no macroscopic percolation of the crystalline BaTiO3 has appeared in our opal matrix. Nevertheless, Raman spectra bring evidence of a diffuse ferroelectric phase transition in the opal-BaTiO3 composite

Research data: Search for nonlinear thz absorption by electromagnons in multiferroic hexaferrites

Datasets measured at the TELBE THz facility consisting of raw (time-sorted) data and binned data that was used for further analysis. The xlsx-file contains measured THz powers. Metadata can be found in labbook file zip archive. Final data analysis was performed by Jakub Vít