New thorium–bismuth oxide solid solutions with oxygen vacancy induced tunable ferromagnetism

Abstract

Ferromagnetism originating from oxygen vacancies could be observed in Th1−xBixO2−δ (0 < x ≤ 0.3) solid solutions. The saturation magnetization was found to increase with Bi concentration as confirmed by magnetic and EPR investigations.

Efficient Use of a Polyamine Carboxylate Ligand to Probe the Extent of Incorporation of Stereochemically Active Bi3+ in ThO2

“…A plot of cubic lattice constants, extracted from successful Le Bail refinements, against the bismuth content revealed an increasing trend (Figure (b). This was similar to the trend noticed for samples obtained by solid state reactions earlier and reaffirmed the +3 oxidation state for bismuth in the samples . The oxygen vacancies introduced as a result of substitution of lower valent Bi 3+ for Th 4+ could provide two different coordination environments for Bi 3+ (VI and VIII fold).…”

“…The evolution of CO 2 from the pyrolysis of these co‐precipitated complexes on heating would be providing a reducing atmosphere in which the bismuth could exist only in +3 oxidation state and not the higher ones viz., +4 or +5. It has been argued earlier based on bond valence sum and other analysis that bismuth existed in +3 oxidation state when substituted in thoria …”

“…The oxygen vacancies introduced as a result of substitution of lower valent Bi 3+ for Th 4+ could provide two different coordination environments for Bi 3+ (VI and VIII fold). This factor could also contribute to the non‐linear variation of cubic lattice constant . The broadening of reflections in pxrd patterns of bismuth containing samples, as compared with pure thoria, suggested the presence of strain in the lattice caused possibly from the higher ionic radius of Bi 3+ (1.17 Å) versus Th 4+ (1.05 Å) in VIII‐fold coordination.…”

“…Solution based routes of making thoria are available in plenty, and synthetic routes for making Bi 2 O 3 employing water a solvent medium suffers from its facile hydrolyzability. Although the solid solution between ThO 2 and δ ‐Bi 2 O 3 has been demonstrated earlier, the recent report of oxygen vacancy induced ferromagnetism in these systems by Kanrar et al . has contributed additional interest warranting more in‐depth investigations.…”

Effects of Nearly‐2D Oxygen Vacancy Clustering on the Magnetic Properties of d0 Systems: The Case of Anatase and Rutile TiO2

“…This hypothesis has been further confirmed by the finding of FM in undoped TiO 2−δ , HfO 2 , and other closed‐shell oxides (CaO, ZnO, SrTiO 3 , MgO, LaAlO 3 , LSAT, Al 2 O 3 ) and non‐oxide materials (AlN, GaN, proton‐irradiated graphite). In this frame, these systems are tentatively regarded as d 0 magnets, though d 0 magnetism is an issue that is still under discussion and not established beyond doubt.…”