Ferromagnetism in Co doped CeO2: Observation of a giant magnetic moment with a high Curie temperature

Abstract

We report room temperature ferromagnetism in single crystal Ce1_ _ A .CoA .0 2__< 5 (xssO.OS) films deposited on a LaAlC^OOl) substrate. Films were grown by a pulsed laser deposition technique and were thoroughly characterized using x-ray diffraction, high-resolution transmission electron microscopy coupled with electron energy loss spectroscopy and scanning transmission electron microscopy-Z contrast, x-ray photoelectron spectroscopy, optical transmission spectroscopy, and magnetic measurements. These films are transparent in the visible regime and exhibit a very high Curie temperature ~740-875 K with a giant magnetic moment. Our results indicate that the ferromagnetic property is intrinsic to the C e02 system and is not a result of any secondary magnetic phase or cluster formation.

Aliovalent doping of CeO2: DFT study of oxidation state and vacancy effects

“…Note that the Shannon crystal radii for Co III and Co IV would be too small, 78,79 showing that the divalent nature, inferred from the calculated radius, supports the experimental suggestion of divalent Co dopants. 30,69,[72][73][74]123 The results for Ba are a bit peculiar, since the calculated radius is significantly lower than either 6-, 7-, or 8-coordinate Shannon crystal radii for divalent Ba. 78,79 Assuming the general trends seen in the Shannon crystal radii for other elements are also valid for Ba (i.e.…”

Concentration dependence of magnetic moment in Ce1-xFexO2

“…In addition to oxygen vacancies, TM doping has been shown to increase the RTFM of ceria NPs (6)(7)(8)(9)(10)(11)(12)(13). There are at least two possible mechanisms for RTFM enhancement by TM doping: creation of oxygen vacancies by introduction of a different-valance dopant into the host lattice and ferromagnetic ordering of a TM dopant.…”

Reversible switching of room temperature ferromagnetism in CeO2-Co nanoparticles

“…CeO 2 -based systems have been thoroughly studied after the discovery of RT-FM on both pure 6,7,8,9,10 and slightly doped 11,12,13,14 samples. A large amount of effort has been devoted to the study of thin films 3,12,13,15,16,17,18,19 (see also references in [1]) while few works have focused on powdered samples 8,9,10,11,14 .…”

“…CeO 2 -based systems have been thoroughly studied after the discovery of RT-FM on both pure 6,7,8,9,10 and slightly doped 11,12,13,14 samples. A large amount of effort has been devoted to the study of thin films 3,12,13,15,16,17,18,19 (see also references in [1]) while few works have focused on powdered samples 8,9,10,11,14 .The use of powders is advantageous because the typically low magnetic signals of these systems can easily be enhanced just by increasing the quantity of the sample. In addition, the surface to volume ratio of the sample can be adjusted simply by performing adequate thermal treatments and this is particularly convenient as the surface is usually the preferred location of point defects.…”

“…The FM contribution is enhanced as we increase the time Among the various oxides displaying this particular behavior is CeO 2 , which in bulk is a diamagnetic insulator with proven capability as an oxygen ion conductor when doped with trivalent Sm or Gd ions 5 . CeO 2 -based systems have been thoroughly studied after the discovery of RT-FM on both pure 6,7,8,9,10 and slightly doped 11,12,13,14 samples. A large amount of effort has been devoted to the study of thin films 3,12,13,15,16,17,18,19 (see also references in [1]) while few works have focused on powdered samples 8,9,10,11,14 .…”