The Magnon Spectrum in the Domain Ferromagnetic State of Antisite Disordered Double Perovskites
arXiv:1204.1194 · doi:10.1103/PhysRevB.88.214428
Abstract
In their ideal structure, double perovskites like Sr_2FeMoO_6 have alternating Fe and Mo along each cubic axes, and a homogeneous ferromagnetic metallic ground state. Imperfect annealing leads to the formation of structural domains. The moments on mislocated Fe atoms that adjoin each other across the domain boundary have an antiferromagnetic coupling between them. This leads to a peculiar magnetic state, with ferromagnetic domains coupled antiferromagnetically. At short distance the system exhibits ferromagnetic correlation while at large lengthscales the net moment is strongly suppressed due to inter-domain cancellation. We provide a detailed description of the spin wave excitations of this complex magnetic state, obtained within a 1/S expansion, for progressively higher degree of mislocation, i.e., antisite disorder. At a given wavevector the magnons propagate at multiple energies, related, crudely, to `domain confined' modes with which they have large overlap. We provide a qualitative understanding of the trend observed with growing antisite disorder, and contrast these results to the much broader spectrum that one obtains for uncorrelated antisites.
References in corpus (7)
- A new class of magnetic materials: Sr2FeMoO6 and related compounds
- Spin Rotation Technique for Non-Collinear Magnetic Systems: Application to the Generalized Villain Model
- Confined spin waves reveal an assembly of nanosize domains in ferromagnetic La(1-x)CaxMnO3 (x=0.17,0.2)
- Antisite Domains in Double Perovskite Ferromagnets: Impact on Magnetotransport and Half-metallicity
- Microscopic model, spin wave theory and competing orders in the double perovskites
- Quantized spin waves in the metallic state of magnetoresistive manganites
- Structural Ordering and Antisite Defect Formation in Double Perovskites