Spin gaps in the ordered states of La$_2$LiXO$_6$ (X = Ru, Os) and their relation to distortion of the cubic double perovskite structure in 4$d^3$ and 5$d^3$ magnets

D. D. Maharaj; G. Sala; C. A. Marjerrison; M. B. Stone; J. E. Greedan; B. D. Gaulin

doi:10.1103/PhysRevB.98.104434

paper

Spin gaps in the ordered states of La $_{2}$ LiXO $_{6}$ (X = Ru, Os) and their relation to distortion of the cubic double perovskite structure in 4 $d^{3}$ and 5 $d^{3}$ magnets

arXiv:1805.10467 · doi:10.1103/PhysRevB.98.104434

Abstract

Time-of-flight inelastic neutron scattering measurements have been carried out on polycrystalline samples of the 4 $d^{3}$ and 5 $d^{3}$ double pervoskite antiferromagnets La $_{2}$ LiRuO $_{6}$ and La $_{2}$ LiOsO $_{6}$ . These reveal the development of an inelastic spin gap in La $_{2}$ LiRuO $_{6}$ and La $_{2}$ LiOsO $_{6}$ of $\sim$ 1.8(8) meV and 6(1) meV, below their respective ordering temperatures, $T_{N}$ , $\sim$ 23.8 K and 30 K. The bandwidth of the spin excitations is shown to be $\sim$ 5.7(9) to 12(1) meV, respectively, at low temperatures. Spin gaps are surprising in such magnets as the t $_{2 g}$ levels of Ru $^{5 +}$ or Os $^{5 +}$ are expected to be half-filled, resulting in an anticipated orbital singlet for both materials. We compare these results in monoclinic double perovskites La $_{2}$ LiRuO $_{6}$ and La $_{2}$ LiOsO $_{6}$ with those in cubic Ba $_{2}$ YRuO $_{6}$ and Ba $_{2}$ YOsO $_{6}$ , as well as with those in the more strongly monoclinic La $_{2}$ NaRuO $_{6}$ , La $_{2}$ NaOsO $_{6}$ , and Sr $_{2}$ ScOsO $_{6}$ , and model the inelastic magnetic scattering with linear spin wave theory using minimal anisotropic exchange interactions. We discuss the possible role of the distortion of the face-centered cubic, double perovskite structure on the spin gap formation and geometric frustration in these materials, and show that $T_{N}$ scales with the top of the spin wave band in all members of these families that display long range order.

arXiv comment11 pages, 11 figures

Spin gaps in the ordered states of La $_{2}$ LiXO $_{6}$ (X = Ru, Os) and their relation to distortion of the cubic double perovskite structure in 4 $d^{3}$ and 5 $d^{3}$ magnets

Abstract

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Spin gaps in the ordered states of La2​LiXO6​ (X = Ru, Os) and their relation to distortion of the cubic double perovskite structure in 4d3 and 5d3 magnets

Abstract

References in corpus (18)

Cited by in corpus (8)

Spin gaps in the ordered states of La $_{2}$ LiXO $_{6}$ (X = Ru, Os) and their relation to distortion of the cubic double perovskite structure in 4 $d^{3}$ and 5 $d^{3}$ magnets