Design and Crystal Growth of Magnetic Double Perovskite Iridates: Ln₂MIrO₆ (Ln = La, Pr, Nd, Sm-Gd; M = Mg, Ni)

Abstract

A series of monoclinic distorted double perovskites of the general formula Ln 2MIrO6 (Ln = La, Pr, Nd, Sm–Gd; M = Mg, Ni) were grown as highly faceted single crystals from a potassium hydroxide flux. The structural distortions and the magnetic interactions in A2BB′O6 double perovskites can be “designed” via a judicious choice of A, B, and B′ cation sizes and by selecting magnetic or nonmagnetic ions to occupy the A, B, and/or B′ sites. A study of the relationship between the number of magnetic ions, the degree of monoclinic distortion, and the resulting magnetic interactions was conducted. Magnetic susceptibility and field dependent magnetization measurements were performed for all synthesized compounds. It was determined that smaller A-site lanthanide cations cause more pronounced monoclinic distortions, resulting in smaller M–O–Ir (M = Mg, Ni) bond angles that correlate with higher magnetic ordering temperatures. The magnetic susceptibility and field dependent magnetization data were both consistent with canted antiferromagnetism for most titled compositions, indicating a possible trend of increased spin canting, and thus increased ferromagnetic-like interactions, as a function of smaller lanthanide A site cation size.

Insulator-to-half metal transition and enhancement of structural distortions in $$\text {Lu}_2 \text {NiIrO}_6$$ double perovskite oxide via hole-doping

“…It is previously established that deviation of 3 d -O-5 d bond angles from the perfect geometry of the high cubic symmetry structure ( ) in a distorted DPOs lead to a strong AFM superexchange coupling between magnetic ions, which results in a FiM ordering 46 , 50 – 54 and large structural distortions enhance the FiM ordering temperature 55 – 57 . Therefore, we displayed the DFT relaxed three peculiar TM-O-Ir bond angles on and octahedron for undoped, Cr-doped, Mn-doped, and Fe-doped LNIO materials in Fig.…”

Relationship between A-site Cation and Magnetic Structure in 3d-5d-4f Double Perovskite Iridates Ln2NiIrO6 (Ln=La, Pr, Nd)

“…The results allow insights into the role superexchange plays in these scarcely studied hybrid 3d-5d-4f compositions with variable A site cations. These materials were previously reported by some of the authors of this manuscript [8] and this study seeks to elucidate the magnetic structure of all three compositions. Several magnetic ordered phases are observed as the different magnetic ions order.…”

“…Neutron powder diffraction measurements were performed on all Ln 2 NiIrO 6 materials to determine the magnetic structure in different temperature regimes. The crystal structures were previously determined with single crystal x-ray diffraction to be P 2 1 /n (#14) [8]. We first begin with the magnetic structure determination of La 2 NiIrO 6 , that is expected to only contain 3d (Ni 2+ ) and 5d (Ir 4+ ) magnetic ion ordering and a non-magnetic 4f ion (La 3+ ).…”

“…Perovskites are one of the most studied solid-state materials due to their modular structure allowing for the incorporation of a wide range of elements, within the limitations outlined by the Goldschmidt tolerance factor [1][2][3][4]. The ability to stabilize a wide variety of elements with different, and often competing, physical properties within the same material makes the perovskite structure a model system to study a rich diversity of magnetic and electronic properties [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24]. Hybrid 3d-5d(4d) based materials that adopt the perovskite structure type host an array of physical properties originating from a delicate balance of interactions.…”

“…Compared to the single perovskite (ABO 3 ) system with only one B site, the double perovskite (A 2 BB"O 6 ) allows for two crystallographically unique sites on which up to three magnetic ions may reside. Most studies of double perovskites limit the number of magnetic cations to one or two, often on the B and B' site for ease of study, although exceptions do exist [8,13]. This allows for the possibility of studying the interaction between superexchange (B-O-B') and supersuperexchange interactions (B-O-B'-O-B), such as that studied in Ca 2 MOsO 6 (M = Co, Ni) [14,17].…”