Volume 108, Number 2, October 2014
|Number of page(s)||4|
|Section||Condensed Matter: Electronic Structure, Electrical, Magnetic and Optical Properties|
|Published online||16 October 2014|
Observation of magnetically hard grain boundaries in double-perovskite Sr2FeMoO6
1 Department of Physics, University of Tokyo - Bunkyo-ku, Tokyo 113-0033, Japan
2 Department of Complexity Science and Engineering, University of Tokyo - Kashiwa, Chiba 277-8561, Japan
3 Department of Quantum Matter, ADSM, Hiroshima University - Higashi-Hiroshima 739-8530, Japan
4 National Synchrotron Radiation Research Center (NSRRC) - Hsinchu 30076, Taiwan
5 Solid State and Structural Chemistry Unit, Indian Institute of Science - Bangalore 560 012, India
Received: 25 July 2014
Accepted: 29 September 2014
Unusual low-temperature magneto-resistance (MR) of ferromagnetic Sr2FeMoO6 polycrystals has been attributed to magnetically hard grain boundaries which act as spin valves. We detected the different magnetic hysteresis curves for the grains and the grain boundaries of polycrystalline Sr2FeMoO6 by utilizing the different probing depths of the different detection modes of x-ray absorption spectroscopy (XAS) and x-ray magnetic circular dichroism (XMCD), namely, the total electron yield (TEY) mode (probing depth ) and the total fluorescence yield (TFY) mode (probing depth ). At 20 K, the magnetic coercivity detected in the TEY mode was several times larger than that in the TFY mode , indicating harder ferromagnetism of the grain boundaries than that of the grains. At room temperature, the grain boundary magnetism became soft and and were nearly the same. From the line-shape analysis of the XAS and XMCD spectra, we found that in the grain boundary region the ferromagnetic component is dominated by Fe2+ or well-screened signals, while the non-magnetic component is dominated by Fe3+ or poorly screened signals.
PACS: 75.60.-d – Domain effects, magnetization curves, and hysteresis / 78.70.Dm – X-ray absorption spectra / 61.72.Mm – Grain and twin boundaries
© EPLA, 2014
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