Observation of a Large Magnetic Anisotropy in the New 2H-Perovskite Related Oxide Ba₈CoRh₆O₂₁:  Magnetic Measurements on Aligned Single Crystals

Abstract

Single crystals of Ba8CoRh6O21, grown out of a potassium carbonate flux, were characterized by single-crystal X-ray diffraction and magnetic measurements. X-ray data were collected in a superspace group approach and solved using the JANA2000 software package. Ba8CoRh6O21 represents the first example of a structurally characterized m = 5, n = 3 member of the A3n+3mA'nB3m+nO9m+6n family of 2H hexagonal perovskite related oxides and contains chains consisting of six consecutive RhO6 octahedra followed by one distorted CoO6 trigonal prism. Magnetic measurements were carried out on large aligned single crystals, and a very large magnetic anisotropy in the magnetic susceptibility, persisting up to room temperature, was observed.

Materials Discovery by Flux Crystal Growth: Quaternary and Higher Order Oxides

“…The only difference in the crystal growth process was the reagents that were used as the Sr sources: SrCO 3 for the former, and SrCl 2 ⋅6 H 2 O for the latter, and it was hypothesized that the Cl − anion in the flux mixture may have favored the formation of the Rh‐rich phase. Long hexagonal rods (Figure 16) of Ba 8 CoRh 6 O 21 82 were prepared by the dissolution of BaCO 3 , Co 3 O 4 , and Rh in a K 2 CO 3 melt at 1050 °C. Another platinum group based oxide, Ca 3 LiRuO 6 ,83 was obtained as dark red hexagonal rods from the polycrystalline material dissolved in a tenfold mass excess of flux, which consisted of a 1:1 mixture of Li 2 CO 3 and K 2 CO 3 .…”

Crystal Growth and Structure Determination of Oxygen-Deficient Sr6Co5O15

“…The structures of these oxides can be described as a result of alternative stacking of m [A 3 O 9 ] layers and n [A 3 A‘O 6 ] layers, followed by filling of the interstitial octahedral B sites. The general formula derived from such stacking is A 3 n +3 m A‘ n B 3 m + n O 9 m +6 n ( m and n are integers), where A is mainly alkaline earth ions, A‘ and B can be almost any element from the periodic table, such as alkali, , alkaline earth, , transition, − or main group metal elements. , Similar to the 2H-perovskite (BaNiO 3 ), the stacking of such layers leads to one-dimensional chains of face-sharing [A‘O 6 ] trigonal prism (TP) and [BO 6 ] octahedra (Oh) along the c axis. , Numerous oxides of this 2H-perovskite-related family have been synthesized; for instance, Ca 3 Co 2 O 6 , Ba 7 PdMn 5 O 18 , Ba 8 CoRh 6 O 21 , Ba 9 Rh 8 O 24 , and Ba 11 Rh 10 O 30 15 are typical compounds, which consist of polyhedral chains repeat of one up nine Oh followed by one TP. The polyhedral chains are well separated by A cation arrays, which can also be considered as A cation chains.…”

Crystal Growth and Structure Determination of Barium Rhodates: Stepping Stones toward 2H−BaRhO3

“…Our group has been working on the synthesis, specifically the single-crystal growth, of compounds in the latter category, aiming at ever-longer sequences of face-sharing octahedra, approaching compositions such as BaRhO 3 . To that end, we have synthesized Sr 6 Rh 5 O 15 , , Ba 8 CoRh 6 O 21 , and Ba 9 Rh 8 O 24 with N prisms / N octahedra values of 1 / 5 , 1 / 6 , and 1 / 7 , respectively. As can be deduced from the N prisms / N octahedra values, the structures are listed with increasingly longer sequences of octahedra in the polyhedral chain.…”