Comparative Study of Potentially J_eff = 0 Ground State Iridium(V) in SrLaNiIrO₆, SrLaMgIrO₆, and SrLaZnIrO₆

Abstract

A series of polycrystalline double perovskites SrLaBIrO 6 (B = Ni, Mg, Zn) containing Ir 5+ (5d 4 ) was synthesized by solid state reactions, and structural, magnetic and electronic properties were investigated. The isotypic fully ordered double perovskites crystallize in space group P2 1 /n and show semiconducting behavior with estimated bandgaps of approximately 0.2 eV for SrLaNiIrO 6 and SrLaZnIrO 6 , 2095 and 0.4 eV for SrLaMgIrO 6 . SrLaNiIrO 6 is an antiferromagnet with a Néel temperature of 74 K (μ eff = 3.3 μ B , θ W = -90 K), whereas SrLaMgIrO 6 and SrLaZnIrO 6 are weakly paramagnetic. All title compounds exhibit a temperature-independent contribution to the measured magnetic susceptibility, which supports the notion for a van-Vlecktype response originating from the Ir 5+ (5d 4 , J eff = 0) ions.

Magnetism of Ir5+ -based double perovskites: Unraveling its nature and the influence of structure

“…Our measurements on Sr 2 YIrO 6 indicate the lack of longrange magnetic order at least to 1.8 K. The magnetization at 014449-5 [15]. Other values reported for Ba 2−x Sr x YIrO 6 and LaSrBIrO 6 samples are also in the 0.16-0.63μ B /Ir range [14,16,26]. On the other hand, Cao et al found higher μ eff (μ eff = 0.91μ B /Ir) as well as long-range magnetic order below 1.8 K [10,11].…”

“…In all those cases in which the magnetic response has been reported to be ascribed to paramagnetic impurities, a small percentage, 5%, has been estimated [13][14][15][16]18]. Following these works, the amount of magnetic centers would be ∼3% in our Sr 2 YIrO 6 sample [estimated from μ eff and assuming Ir 4+ ions, this value is smaller if estimated from M(H ) data].…”

“…This has not only basic scientific interest but also undoubted practical potential in spintronics. Consequently, interest in 5d 4 magnetism has been boosted following this publication [11][12][13][14][15][16][17][18][19].…”

“…Several experimental groups have proposed that the magnetism observed in their Sr 2−x Ba x YIrO 6 samples is ascribed to Ir 6+ and/or Ir 4+ paramagnetic impurities (estimated to be <5% in all cases) [12][13][14][15][16]18] caused by chemical disorder and/or off-stoichiometry. While the presence of Ir 6+ and/or Ir 4+ impurities cannot be a priori ruled out, identifying them as the origin of magnetic correlations is not without controversy.…”

Doped Sr2FeIrO6—Phase Separation and a Jeff ≠ 0 State for Ir5+

“…Indeed many phases containing Ir 5+ O 6 centers are observed to have very small moments. [7][8] However there are a number of studies which report non-zero moments for Ir 5+ cations, which are not easily dismissed as being due to impurity phases. [9][10][11][12] The appearance of these J eff ≠ 0 states has been attributed to local distortions in the IrO 6 coordination weakening the SOC interaction, 13 or band structure effects arising from superexchange coupling.…”