Magnetic excitation spectra in pyrochlore iridates

作者：Lee Eric Kin Ho^*; Bhattacharjee Subhro; Kim Yong Baek

来源：Physical Review B, 2013, 87(21): 214416.

DOI：10.1103/PhysRevB.87.214416

Metal-insulator transitions in pyrochlore iridates (A(2)Ir(2)O(7)) are believed to occur due to subtle interplay of spin-orbit coupling, geometric frustration, and electron-electron interactions. In particular, the nature of magnetic ordering of iridium ions in the insulating phase is crucial for the understanding of several exotic phases recently proposed for these materials. We study the spectrum of magnetic excitations in the intermediate-coupling regime for the so-called all-in/all-out magnetic state in pyrochlore iridates with nonmagnetic A-site ions (A = Eu,Y). This state was found to be preferred in previous theoretical studies. We find that the effect of charge fluctuations on the magnetic excitations in the intermediate-coupling regime leads to a strong departure from the lowest-order spin-wave calculations based on spin models obtained in the strong-coupling limit. We discuss the characteristic features of the magnetic excitation spectrum that can lead to conclusive identification of the magnetic order in future resonant inelastic x-ray (or neutron) scattering experiments. This knowledge about the nature of magnetic order and its low-energy features may also provide useful information on the accompanying metal-insulator transition.

• 出版日期2013-6-13