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Spontaneous ferromagnetism at room temperature in oxygen-rich dicalcium cuprate Ca2CuO3+δ

Published online by Cambridge University Press:  31 January 2011

Mahjoub A. Abdelgadir ,
Richard S. Burrows  and
Darl H. McDaniel
Mahjoub A. Abdelgadir*
Affiliation:
Department of Physics, North Carolina A/T State University, Greensboro, North Carolina 27411
Richard S. Burrows
Affiliation:
Department of Chemistry, University of Cincinnati, Cincinnati, Ohio 45221
Darl H. McDaniel
Affiliation:
Department of Chemistry, University of Cincinnati, Cincinnati, Ohio 45221
*
(a) Author to whom correspondence should be addressed.
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Abstract

Stoichiometric Ca2CuO3, having square-planar Cu-chains [C. L. Teske and H. Müller-Buschbaum, Z. Anorg. Allg. Chem. 379, 234 (1970); M. Hjorth and J. Hyldtoft, Acta Chem. Scand. 44, 516 (1990)], is expectedly antiferromagnetic due to 1D intrachain superexchange [K. Okuda, S. Noguchi, K. Konishi, H. Deguchi, and K. Takeda, J. Magn. Magn. Mater. 104–107, 817 (1992)]. Nonetheless, we report remarkable spontaneous ferromagnetism at 293 K after sintering, prominently in oxygen. This apparently introduced excess oxygen at vacant quasioctahedral sites, promoting spin-flip and ferromagnetic interchain coupling. Thermogravimetry (TGA) revealed excess oxygen, ≈0.17 O/Cu. X-ray diffraction (XRD) yielded a comparatively smaller unit cell. Ferromagnetism disappeared by oxygen depletion, mimicking reported nonmagnetism of Ca2CuO3−δ [Okuda et al. (1992)]. Elemental analysis showed insignificant magnetic impurity traces. Tc ranged between 680 K and 723 K, depending on freshness and purity. Saturation magnetization varied with processing, optimally 0.30 A · m2/kg at 1.0 T applied field. Coercivity and remanence varied with purity.

Type
Articles
Information
Journal of Materials Research , Volume 11 , Issue 7 , July 1996 , pp. 1804 - 1809
Copyright
Copyright © Materials Research Society 1996

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References

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