Edwin Kermarrec, McMaster University

Jeudi 18 Décembre 2014, 10h30
Amphi Boreau, Esc C, 2ème etage

Exotic magnetism on the frustrated FCC lattice of 4d and 5d double perovskites

Edwin Kermarrec
McMaster University — Department of Physics & Astronomy

In the search for new exotic quantum states, the impact of strong spin-orbit interaction has been recently underlined with the discovery of the Jeff = ½ spin-orbital Mott state in the 5d5 layered perovskites iridates [1]. The double perovskite structure, where the magnetic ions form a face-centered-cubic (fcc) sublattice, can accommodate a large variety of 5d transition metal elements, and therefore offers an ideal playground for systematic studies of the exotic magnetic and non-magnetic ground states stabilized by strong spin-orbit coupling [2].
Here, we report time-of-flight neutron scattering measurements on the antiferromagnetic, frustrated, cubic double perovskite system Ba2YOsO6 [3]. Its non-distorted fcc lattice is decorated with magnetic Os5+ (5d3) ions which undergo a magnetic transition to a type I fcc long range ordered antiferromagnetic state below TN = 70 K. Our inelastic data reveals a large spin gap to the spin-wave excitations ∆ = 17 meV, unexpected for an orbitally quenched, d3 electronic configuration. We will discuss our results in the context of other recently studied cubic double perovskites, where exotic magnetic and non-magnetic phases are expected.

[1] B. J. Kim et al., Phys. Rev. Lett. 101, 076402 (2008).
[2] G. Chen, R. Pereira and L. Balents, Phys. Rev. B, 82, 174440 (2010).
G. Chen and L. Balents, Phys. Rev. B, 84, 094420 (2011).
[3] E. Kermarrec et al., arXiv:1410.0725 (2014).

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