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Effect of geometry on the magnetic properties of CoFe₂O₄–PbTiO₃ multiferroic composites

Wang, B. Y., Wang, H. T., Singh, Shashi B., Shao, Y. C., Wang, Y. F., Chuang, C. H., Yeh, P. H., Chiou, J. W., Pao, C. W., Tsai, H. M., Lin, H. J., Lee, J. F., Tsai, C. Y., Hsieh, W. F., Tsai, M.-H., Pong, W. F.
RSC advances 2013 v.3 no.21 pp. 7884-7893
X-radiation, X-ray absorption spectroscopy, cations, circular dichroism spectroscopy, cobalt, compression strength, geometry, hysteresis, iron, magnetic properties, magnetism, powders
In this study, X-ray absorption near-edge structure (XANES), extended X-ray absorption fine structure (EXAFS), X-ray magnetic circular dichroism (XMCD) and element- and site-specific magnetic hysteresis (ESMH) are used to elucidate the effect of geometry (0-3- and 2-2-type) on the magnetic properties of CoFe₂O₄–PbTiO₃ (CFO–PTO) multiferroic composites by comparison with those of the reference CFO and PTO powders. Magnetic Co ions in CFO have been confirmed to be located at both the tetrahedral (A)- and octahedral (B)-sites. CFO retains its mixed-spinel structure as verified by the EXAFS, XMCD and ESMH measurements. ESMH measurements further demonstrate that the magnetic moments of Co²⁺ and Fe³⁺/Fe²⁺ cations at both the A- and B-sites in the composites are smaller than those of the CFO powder. The reduction of the magnetic moments in the 2-2-type composite was larger than that in the 0-3-type composite. The reduction of the magnetic moments in the composites was attributable to the formation of anti-phase boundaries owing to the compressive strain in CFO, which is the largest strain in the 2-2-type composite. Based on the Ti L₃,₂-edge XMCD measurements of the CFO–PTO composites, no induced magnetic moment was observed at the Ti sites in the PTO matrix, excluding the possibility that the Ti ions in the PTO matrix affect the magnetic properties of these CFO–PTO composites.