Abstract: | In addition to the well known ferromagnetism, double perovskites are also
expected to exhibit antiferromagnetic (AF) order driven by electron
delocalisation. This has been seen in model Hamiltonian studies and confirmed
via ab initio calculations. The AF phases should occur, for example, on
sufficient electron doping of materials like Sr2FeMoO6 (SFMO) via La
substitution for Sr. Clear experimental indication of such AF order is limited,
possibly because of increase in antisite disorder with La doping on SFMO,
although intriguing signatures of non ferromagnetic behaviour are seen. We
study the survival of electronically driven antiferromagnetism in the presence
of spatially correlated antisite disorder in a two dimensional model
and extract the signals in magnetism
and transport. We discover that A and G type AF order, that is predicted in
the clean limit, is actually suppressed less strongly than ferromagnetism
by antisite disorder. The AF phases are metallic, and, remarkably, more conducting
that the ferromagnet for similar antisite disorder. We also highlight the phase
coexistence window that connects the ferromagnetic regime to the A type
antiferromagnetic phase, and comment on the situation in three dimensions. |