Berlin 2005 – wissenschaftliches Programm
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MA: Magnetismus
MA 20: Poster:Schichten(1-29),Spintrsp(30-45),Ex-Bias(46-63),Spindyn(64-75),Mikromat.(76-80),Cluster(81-94),Abbv.(95-99),Obflm(100-02),SpElek.(103-09),E-Theo(110-14),Mikromag.(115-16),Spin+PÜ(117-26),Mag.Mat.(127-51),Meth.(152-55),Mol.Mag(156-59),Kondo(160-65
MA 20.136: Poster
Montag, 7. März 2005, 14:00–18:00, Poster TU C
Ferrimagnetism in the Brownmillerit compounds Sr2M2O5 M = Fe, Co — •Franziska Emmerling, Gerhard H. Fecher, Vadim Ksenofontov und Claudia Felser — Johannes Gutenberg - Universität, D-55099 Mainz, Germany
The oxides Sr2M2O5 (M=Fe, Co) were prepared via ceramic and sol-gel methods. The samples were characterized by X-ray diffraction, SQUID magnetometry, XPS- and Mößbauer spectroscopy. The XRD diffraction patterns confirmed that, at least within the sensitivity of XRD, the samples are single phase with the expected lattice parameter (Ima2, a=15.66/15.59 Å, b=5.56/5.66 Å, c=5.46/5.53ÅCo/Fe). SQUID measurements revealed a total magnetic moment of 0.34 (Co) and 0.46 (Fe) µB. The 57Fe Mößbauer spectrum of Sr2Fe2O2 indicates the two expected Fe positions and points on magnetic order at room temperature.
The electronic structures were calculated using the self-consistent, linearized muffin-tin orbital (LMTO) program of Anderson at al. The calculations revealed a ferrimagnetic ordering with magnetic moments of 1.30 (Co)/2.67 (Fe) for the octahedral coordinated A-site and 1.29 (Co)/2.90 (Fe) for the tetrahedral coordinated B-site and a resulting moment of 0.215(Co)/ 0.94 (Fe) µB.
The series Sr2Co2−xFexO5 with varying Co to Fe ratio x will be discussed on hand of experimental data and calculated results.