Rajan, K. Jayanthi and Ganesan, Kausalya and Lanka, Satyanaryana and Bishnoi, Swati and Sunkara, Manorama V.
(2016)
Probing high temperature ferromagnetism and its paramagnetic phase change due to Eu3+ incorporation in ZnO nanophosphors.
RSC Advances , 6 (79).
75669-75680.
ISSN 2046-2069
Abstract
Ferromagnetic oxide semiconductors exhibiting efficient luminescent properties together with robust ferromagnetism above room temperature form an exclusive class of spintronic materials endowed with both charge and spin degrees of freedom. Herein, we report on the occurrence of high temperature ferromagnetism (>600 K) in zinc oxide nanophosphors attributed to the presence of defects in the host lattice and wherein incorporation of rare earth ions contributed to a gradual reduction in the ferromagnetic character and steady transformation to paramagnetic behavior. Although undoped ZnO nanophosphors exhibit a high coercive field and saturation magnetization along with a prominent green emission (536 nm) attributed to the presence of oxygen vacancies V-o, Eu3+ doping results in a decrease in green emission along with coercivity as well as magnetization efficient line emission in the orange red region (618-622 nm) pointing to a definite correlation between the V-o and ferromagnetism. The temperature dependence of the magnetization shows stable ferromagnetism with Curie temperature above 600 K for undoped ZnO and a ferromagnetic to paramagnetic transition with an increase in Eu3+ concentration that has been explained through an F+ center exchange mechanism.
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