The Crystal Structure and Magnetic Behavior of Quinary Osmate and Ruthenate Double Perovskites LaABB′O₆ (A = Ca, Sr; B = Co, Ni; B′ = Ru, Os)

Abstract

Six La ABB'O ( A = Ca, Sr; B = Co, Ni; B' = Ru, Os) double perovskites were synthesized, several for the first time, and their crystal structures and magnetic behavior were characterized with neutron powder diffraction and direct-current and alternating-current magnetometry. All six compounds crystallize with P2 /n space group symmetry, resulting from a a c octahedral tilting and complete rock salt ordering of transition-metal ions. Despite the electronic configurations of the transition-metal ions, either d-d or d-d, not one of the six compounds shows ferromagnetism as predicted by the Goodenough-Kanamori rules. LaSrNiOsO, LaSrNiRuO, and LaCaNiRuO display long-range antiferromagnetic order, while LaCaNiOsO, LaCaCoOsO, and LaSrCoOsO exhibit spin-glass behavior. These compounds are compared to the previously studied LaCaCoRuO and LaSrCoRuO, both of which order antiferromagnetically. The observed variations in magnetic properties can be attributed largely to the response of competing superexchange pathways due to changes in B-O- B' bond angles, differences in the radial extent of the 4d ( B' = Ru) and 5d ( B' = Os) orbitals, and filling of the t orbitals of the 3d ion.

Structure and magnetism of the Rh4+-containing perovskite oxides La0.5Sr0.5Mn0.5Rh0.5O3and La0.5Sr0.5Fe0.5Rh0.5O3

“…Table 3, with selected bond lengths listed in Table 4. SXRD data provide no evidence for Fe/Rh cation-order, with a model based on the reported cation-ordered structure of LaSrNiRuO 6 (space group P2 1 /n) 11 reverting to a disordered structure when the Fe and Rh occupancies were refined.…”

“…6,7 In a broader context the inter-cation magnetic couplings in mixed 3d/4d and 3d/5d perovskite oxides do not generally appear to follow the Goodenough Kanamouri rules 8 which dominate 3d systems. [9][10][11] However, to date only a subset of the 3d/4d and 3d/5d perovskite oxide phases which could be envisioned have been reported, 12 so it is hard to formulate broad magnetic coupling rules for this class of compound. To help address this situation, we have been studying mixed perovskite phases containing rhodium.…”

Hexagonal Perovskites as Quantum Materials

“…In classical double perovskites, there are two different "M type" ions in an ordered array or a partially ordered array within the MO3 framework. Double perovskites can be written in the form A2MM'O6, where M and M' can be different ions such as in Sr2FeWO6, a material that has a particularly high magnetoresistance 51 or even the same M metal with different oxidation states, such as is seen in BaBiO3 (Ba2Bi 3+ Bi 5+ O6 formally) [52][53][54][55][56][57] , the basis for superconductivity in several perovskite oxides 58,59 . Disordered and partially ordered M-M' double perovskites are known.…”

Long- and short-range magnetism in the frustrated double perovskite Ba2MnWO6

“…primarily affects lattices which consist of connecting triangular plaquettes, such as planar kagome lattices, pyrochlores and the face-centred cubic (fcc) structure [1]. Geometrical frustration can result in a number of novel states such as spin glass [2,3], spin ice [4,5] spin liquids [6,7] and other complex states such as the valence bond glass [8,9]. Frustration has also been shown to cause unexpected behaviour above the Néel temperature (TN), where short range correlations can take place [10,11].…”