Frustrated fcc antiferromagnetBa2YOsO6: Structural characterization, magnetic properties, and neutron scattering studies

Abstract

We report the crystal structure, magnetization and neutron scattering measurements on the double perovskite Ba2YOsO6. The F m3m space group is found both at 290 K and 3.5 K with cell constants a0 = 8.3541(4)Å and 8.3435(4)Å, respectively. Os 5+ (5d 3 ) ions occupy a non-distorted, geometrically frustrated face-centered-cubic (FCC) lattice. A Curie-Weiss temperature θ = −772 K suggests the presence of a large antiferromagnetic interaction and a high degree of magnetic frustration. A magnetic transition to long range antiferromagnetic order, consistent with a Type I FCC state below TN ∼ 69 K, is revealed by magnetization, Fisher heat capacity and elastic neutron scattering, with an ordered moment of 1.65(6) µB on Os 5+ . The ordered moment is much reduced from either the expected spin only value of ∼ 3µB or the value appropriate to 4d 3 Ru 5+ in isostructural Ba2YRuO6 of 2.2(1) µB, suggesting a role for spin orbit coupling (SOC). Triple axis neutron scattering measurements of the order parameter suggest an additional first-order transition at T = 67.45 K, and the existence of a second ordered state. Time-of-flight inelastic neutron results reveal a large spin gap ∆ ∼ 17 meV, unexpected for an orbitally quenched, d3 electronic configuration. We discuss this in the context of the ∼ 5 meV spin gap observed in the related Ru 5+ , 4d 3 cubic double perovskite Ba2YRuO6, and attribute the ∼ 3 times larger gap to stronger SOC present in this heavier, 5d, osmate system.

The role of nonmagnetic d0 vs. d10 B-type cations on the magnetic exchange interactions in osmium double perovskites

“…Investigations into double perovskites with single Os 5+ magnetic sublattice will provide help for a better understanding of the remarkable magnetic properties of osmium double perovskites, such as the exceptionally high-temperature ferrimagnetism in Sr 2 CrOsO 6 [2] and the strikingly different magnetic properties between Sr 2 FeOsO 6 [12,13] and Ca 2 FeOsO 6 [3,7]. Most of the well-studied double perovskites with nonmagnetic B cations and Os 5+ forming the B′ sublattice known so far display AFM transitions [16][17][18][19][20][21][22][23]. Because the magnetic interactions between the nearest-neighbor (NN) Os 5+ ions are usually thought to run mainly via the Os 5+ -O-O-Os 5+ path [16,17,20,22], the nonmagnetic B cations are not expected to play an important role in the magnetic exchange interactions.…”

“…The synthesis of Ba 2 ScOsO 6 and Ba 2 InOsO 6 was firstly reported by Slight et al [25]; however, to the best of our knowledge, details of their magnetic properties are not known to date. The synthesis and magnetic properties of Ba 2 YOsO 6 were published by Kermarrec et al [23]. KClO 4 (>99.5%, Kishida Chemical Co., Ltd.).…”

Structural and magnetic properties of the5d2double perovskitesSr2BReO6(Aczel1, Zhao2, Calder3 et al. 2016Phys. Rev. B223244View full textAdd to dashboardCite

“…The 5d 5 DPs that have been studied in detail, including La 2 MgIrO 6 and La 2 ZnIrO 6 , are effective J = 1/2 candidates [9] that exhibit antiferromagnetic ground states and interesting magnetic excitations [10,11]. Materials composed of magnetic ions with 4d 3 /5d 3 electron configurations generally host ordered magnetic ground states also [12][13][14][15][16][17]. Aside from a few known exceptions [18,19], the spin arrangements in d 3 systems are usually well-accounted for by mean field theory, with ground state selection arising from the signs and magnitudes of the nearest neighbor and next nearest neighbor exchange interactions [20].…”

Magnetic order and electronic structure of the5d3double perovskiteSr2ScOsO6

“…[15] they find that the electronic state may lie between L-S and J-J coupling regimes, and therefore the t 2g 3 assumption is invalid. Recent experimental investigations have therefore discussed the role of SOC in 4d 3 and 5d 3 double perovskites [9,[16][17][18][19]. Here we investigate the magnetic insulator Sr 2 ScOsO 6 , which has one of the highest known magnetic transition temperatures in double perovskites hosting only one magnetic ion [20,21].…”

“…Despite high frustration indexes |Θ|/T N , most of these systems overcome frustration to order in a type I AFM state at low temperature [see Fig. 3(d)], although some show short range incommensurate order or type III order [11,13,16,18,36,37]. Sr 2 ScOsO 6 , Sr 2 YOsO 6 and Ba 2 YOsO 6 all host long range type I AFM order, with T N s of 95 K, 53 K and 69 K, and frustration indexes |Θ|/T N = 7.4, 6.4 and 11 respectively [13,18].…”