Mn4+ emission in pyrochlore oxides

Magnetic pyrochlore oxides

Within the past 20 years or so, there has occurred an explosion of interest in the magnetic behavior of pyrochlore oxides of the type A 2 B 4+ 2 O7 where A is a rare-earth ion and B is usually a transition metal. Both the A and B sites form a network of corner-sharing tetrahedra which is the quintessential framework for a geometrically frustrated magnet. In these systems the natural tendency to...

Monte Carlo Study of the Pyrochlore Double-Exchange Model –Frustration Effects in Molybdenum Pyrochlore Oxides–

where t is the transfer integral for nearest-neighbor sites hiji on the pyrochlore lattice, JH represents the Hund’s-rule coupling between the itinerant electron spin ~si and the localized spin ~ Si, while JAF is the super-exchange antiferromagnetic interaction between the neighboring localized spins. The first two terms induce the double-exchange ferromagnetic interactions through the kinetic ...

Explorer Breathing Pyrochlore Lattice Realized in A - Site Ordered Spinel Oxides

Breathing pyrochlore lattice realized in A-site ordered spinel oxides LiGaCr4O8 and LiInCr4O8.

A unique type of frustrated lattice is found in two A-site ordered spinel oxides, LiGaCr(4)O(8) and LiInCr(4)O(8). Because of the large size mismatch between Li(+) and Ga(3+)/In(3+) ions at the A site, the pyrochlore lattice, made up of Cr(3+) ions carrying spin 3/2, becomes an alternating array of small and large tetrahedra, i.e., a "breathing" pyrochlore lattice. We introduce a parameter, the...

Electronic structure and exchange interactions in the manganese-based pyrochlore oxides

We describe the ferromagnetism in the manganese pyrochlores, such as Tl2Mn2O7 and Sc2Mn2O7 , in terms of the interplay between superexchange, Zener double exchange, and indirect exchange, the first being antiferromagnetic ~AF! while the last two are ferromagnetic. The tendency towards the antiferroalignment of the localized Mn spins is significantly weakened due to ~i! the presence of spin frus...