X-ray diffraction, Mössbauer spectroscopy, neutron diffraction, optical absorption and ab-initio calculation of magnetic process in orthorhombic YFexCr(1-x)O3 (0 ≤ x ≤ 1) compounds
YFexCr(1-x)O3 (0 ≤ x ≤ 1) compounds prepared by autocombustion were studied with X-ray and neutron powder diffraction, Mössbauer spectroscopy and ab-initio electronic structure calculations to try to understand the interplay of magnetic order and structural parameters as a function of doping in this multiferroic material. All samples exhibit the orthorhombic nuclear structure (space group symmetry Pnma) and the cell parameters vary continuously as a function of doping. In the neutron powder diffraction patterns it was observed that in addition to the Pnma nuclear structure peaks reflections are seen in all samples which arise from magnetic order. These peaks can be indexed using the nuclear unit cell indicating an ordering vector of k = (0,0,0). Using representational analysis and Rietveld refinements the magnetic structure was determined to be Pn’ma’ and the mean magnetic moment per transition metal atom was observed to decrease continuously from Fe to Cr. For compounds with x > 0.25 a weak ferromagnetic contribution is also present which is due to a small canting of the moments out of the basal plane. The Mössbauer spectra corroborate the NPD results with all samples showing single magnetic sextets at 4.2 K. The energy gap and the main direct interband transition of the endmember samples were obtained by optical absorption measurements. These optical data were analyzed with the help of DFT band structure calculation using the GGA-PBE + U approximation.
KeywordsCombustion method Preparation and characterization of YFexCr(1-x)O3 (0 ≤ x ≤ 1) Antiferromagnetism Weak ferromagnetism Mössbauer spectroscopy Neutron powder diffraction
Prof. Dr. F. Wagner for his support in the measurement of the Mössbauer spectra from the Technische Universität München, Germany and Dr. Karla Santacruz G. from the Universidad de Sonora, Mexico for the TEM images. We also appreciate Prof. Manuel Hernández from the Universidad Nacional Autónoma de México (UNAM) for the optical absorption measurements. A portion of this research used resources at the High Flux Isotope Reactor, a DOE Office of Science User Facility operated by the Oak Ridge National Laboratory.
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