Ferromagnetism in un-doped cerium oxide (CeO2) prepared by sol-gel route and annealed in different conditions
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MIHALACHE, Valentina, CIOANGER, M., CERNEA, M., SECU, Mihail. Ferromagnetism in un-doped cerium oxide (CeO2) prepared by sol-gel route and annealed in different conditions. In: Materials Science and Condensed Matter Physics, Ed. 8-th Edition, 12-16 septembrie 2016, Chişinău. Chişinău: Institutul de Fizică Aplicată, 2016, Editia 8, p. 255. ISBN 978-9975-9787-1-2.
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Materials Science and Condensed Matter Physics
Editia 8, 2016
Conferința "International Conference on Materials Science and Condensed Matter Physics"
8-th Edition, Chişinău, Moldova, 12-16 septembrie 2016

Ferromagnetism in un-doped cerium oxide (CeO2) prepared by sol-gel route and annealed in different conditions


Pag. 255-255

Mihalache Valentina, Cioanger M., Cernea M., Secu Mihail
 
National Institute of Materials Physics Bucharest-Magurele
 
Disponibil în IBN: 2 august 2019


Rezumat

Oxides with Curie temperature, TC, exceeding room temperature, are viewed as potential candidates for spintronics that use both charge and spin with resulting functionalities viable for magneto-optic and other devices. Even though many reports of room temperature ferromagnetism, RTFM, on different overwise nonmagnetic oxides are available in literature its origin is still an open question. Within this work the RTFM of un-doped CeO2 was studied. The nanosized CeO2 powders were produced by sol-gel route. The as-prepared material  was annealed, at 500oC and 1015oC for 2h - 11h in an atmosphere of 95%Ar and 5% H2 and in air, in both powder and bulk form. The occurrence of long range ferromagnetic ordering strongly depends on the annealing conditions. The as-prepared powder is not ferromagnetic whereas all treated samples show RTFM. The highest saturation magnetization (~ 10-2 emu/g) was reached on the bulk CeO2 treated in Ar5% H2 for long time. The highest coercivity (~150 Oe) was achieved on a treated at 1015oC in Ar5% H2 and then ground sample.  The as-prepared powder annealed at high temperatures shows near zero coercivity. Curie temperature reached 447oC for samples annealed in air and 587oC for samples annealed in Ar5%H2. No clear dependence of FM on the particle/grain size (SEM/XRD), on the oxidation and reduction processes, or on the presence of defects or adsorbed species (FTIR) on the CeO2 surface was evidenced.