On the possibility of excitonic magnetism in Ir double perovskites

Pajskr, Karel; Novák, P.; Pokorný, Vladislav; Kolorenč, Jindřich; Arita, Ryotaro; Kuneš, J.

doi:10.1103/physrevb.93.035129

Cited by 51 publications

(55 citation statements)

References 24 publications

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“…Our experimental results on single crystal XRD are in good agreement with the theoretical paper reported by Pajskr et al [22], which claims that the noncubic crystal field of Sr 2 YIrO 6 is found to be rather weak and that this compound is quite similar in terms of structure and low-energy properties to the cubic Ba 2 YIrO 6 analog [35].…”

Section: Resultssupporting

confidence: 82%

Iridium double perovskite Sr2YIrO6 : A combined structural and specific heat study

et al. 2017

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Recently, the iridate double perovskite Sr 2 YIrO 6 has attracted considerable attention due to the report of unexpected magnetism in this Ir 5+ (5d 4 ) material, in which according to the J eff model, a nonmagnetic ground state is expected. However, in recent works on polycrystalline samples of the series Ba 2−x Sr x YIrO 6 no indication of magnetic transitions have been found. We present a structural, magnetic, and thermodynamic characterization of Sr 2 YIrO 6 single crystals, with emphasis on the temperature and magnetic field dependence of the specific heat. As determined by x-ray diffraction, the Sr 2 YIrO 6 single crystals have a cubic structure, with space group F m3m. In agreement with the expected nonmagnetic ground state of Ir 5+ (5d 4 ) in Sr 2 YIrO 6 , no magnetic transition is observed down to 430 mK. Moreover, our results suggest that the low-temperature anomaly observed in the specific heat is not related to the onset of long-range magnetic order. Instead, it is identified as a Schottky anomaly caused by paramagnetic impurities present in the sample, of the order of n ∼ 0.5(2)%. These impurities lead to non-negligible spin correlations, which nonetheless, are not associated with long-range magnetic ordering.

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Section: Resultssupporting

confidence: 82%

Iridium double perovskite Sr2YIrO6 : A combined structural and specific heat study

et al. 2017

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“…It is of interest that the simple electronic structure calculations employed here, in which only a basic electronic model have been applied, yield moments that are consistent with the experimental observations. We expect that recent, much more sophisticated calculations [29] will yield more detailed insight into the electronic and magnetic behavior of this system.…”

Section: Resultsmentioning

confidence: 99%

Influence of structural distortions on the Ir magnetism in Ba2−xSrxYIrO6 double perovskites

Phelan

Seibel

Badoe

et al. 2016

Solid State Communications

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We explore the relative strengths of spin orbit coupling and crystal field splitting in the Ir 5+ compounds Ba 2-x Sr x YIrO 6 . In the case of strong spin orbit coupling and regular Ir 5+ octahedra, one expects a nonmagnetic J = 0 state; in the case of distorted octahedra where crystal field effects dominate, the t 2g manifold splits into a magnetic ground state. We report the results of continuously transitioning from the cubic Ba 2 YIrO 6 double perovskite with ideal octahedra to the monoclinic Sr 2 YIrO 6 double perovskite with distorted octahedra. We see no emergence of an enhanced Ir 5+ magnetic moment in the series on increasing the structural distortions, as would have been the case for significant crystal field splitting. The near-constant magnetic moment observed through the Ba 2-x Sr x YIrO 6 series reinforces the notion that spin-orbit coupling is the dominant force in determining the magnetism of iridium-oxygen octahedra in perovskitelike structures.

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“…al. 5 rebutted this claim using dynamical mean field theory (DMFT) to obtain a non-magnetic ground state. Furthermore, this study estimated the gap between the J = 0 singlets and the J = 1 triplets to be more than 250 meV which marginalizes the prospect of condensation.…”

Section: 10mentioning

confidence: 99%

Magnetism out of antisite disorder in the J=0 compound Ba2YIrO6

et al. 2017

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We systematically investigate the magnetic properties and local structure of Ba2YIrO6 to demonstrate that Y and Ir lattice defects in the form of antiphase boundary or clusters of antisite disorder affect the magnetism observed in this d 4 compound. We compare the magnetic properties and atomic imaging of (1) a slow cooled crystal, (2) a crystal quenched from 900• C after growth, and (3) a crystal grown using a faster cooling rate than the slow cooled one. Atomic imaging by scanning transmission electron microscopy (STEM) shows that quenching from 900• C introduces antiphase boundary to the crystals, and a faster cooling rate during crystal growth leads to clusters of Y and Ir antisite disorder. STEM study suggests the antiphase boundary region is Ir-rich with a composition of Ba2(Y1−xIrx)IrO6. The magnetic measurements show that Ba2YIrO6 crystals with clusters of antisite defects have a larger effective moment and a larger saturation moment than the slow-cooled crystals. Quenched crystals with Ir-rich antiphase boundary shows a slightly suppressed saturation moment than the slow cooled crystals, and this seems to suggest that antiphase boundary is detrimental to the moment formation. Our DFT calculations suggest magnetic condensation is unlikely as the energy to be gained from superexchange is small compared to the spin-orbit gap. However, once Y is replaced by Ir in the antisite disordered region, the picture of local non-magnetic singlets breaks down and magnetism can be induced. This is because of (a) enhanced interactions due to increased overlap of orbitals between sites, and, (b) increased number of orbitals mediating the interactions. Our work highlights the importance of lattice defects in understanding the experimentally observed magnetism in Ba2YIrO6 and other J = 0 systems.

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On the possibility of excitonic magnetism in Ir double perovskites

Cited by 51 publications

References 24 publications

Iridium double perovskite Sr2YIrO6 : A combined structural and specific heat study

Iridium double perovskite Sr2YIrO6 : A combined structural and specific heat study

Influence of structural distortions on the Ir magnetism in Ba2−xSrxYIrO6 double perovskites

Magnetism out of antisite disorder in the J=0 compound Ba2YIrO6

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