Crystal structures, magnetic properties, and DFT calculation of B-site defected 12L-perovskites Ba2La2MW2O12 (M = Mn, Co, Ni, Zn)

The synthesis, crystal structures and magnetic properties of Ba2La2MW2O12 (M = Mn, Co, Ni, Zn) were investigated. They crystallize in the 12-layer polytype of the perovskite structure with a regular cation defect in the B-site. The results of neutron diffraction measurements reveal that they adopt a rhombohedral structure with a space group R - 3 and have a cation ordering between Ba and La ions in the A-site. In these compounds, the magnetic M ions form the 2D triangular lattice. From the results of magnetic measurements, the ferromagnetic ordering of M2+ ions for M = Co (T-C = 1.3 K) and Ni (6.2 K) and the paramagnetic behavior (T > 1.8 K) with an antiferromagnetic interaction for M = Mn are observed. From the DFT calculation, their band structures and magnetic interactions are discussed

Crystal and Magnetic Structures of La2CoPtO6 Double Perovskite

We investigated the crystal structure and magnetic structure in cobaltite-platinate double perovskite of La2CoPtO6, employing various techniques of X-ray diffraction, neutron diffraction, and the extended X-ray absorption fine structure analysis. It is shown that the crystal symmetry is maintained as P21/n in the temperature range of 0.03 Å) of the Co-Co networks, the system is not subject to spin frustration effect. Details in the magnetic structure are determined; at 12 K, the Co magnetic moment was (0.8, 0, 2.7) Bohr magneton, the magnetic propagation vector was (-0.5, 0, 0.5), and the magnetic symmetry was preferably Δ1(Ag). © 2018 American Chemical Societ

Magnetoelastic octahedral breathing mode in the ferrimagnetic L a2CoIr O6 double perovskite

Distortion of transition-metal ion-oxygen octahedra in perovskite structure has been a long standing subject for exploring the physics of charge-orbital-spin-lattice couplings. Recent findings in nickelates or BaBiO3 have suggested that a charge disproportionation in the transition-metal ions can evoke certain cooperative breathing distortions (CBD), constituted by the symmetric expansion and shrinkage of the octahedra in contrast to the Jahn-Teller-type asymmetric distortion. A double perovskite ferrimagnet, La2CoIrO6 bears inherently the charge disproportionation in the cationic sites with Co2+ and Ir4+ sublattices. In light of seeking the clues for the CBD and its coupling to the magnetic order, the crystal structure and magnetic structure of La2CoIrO6 were examined at various temperatures by using neutron diffraction. Structure refinements and mode decomposition analyses revealed that, indeed, a CBD mode exists substantially in La2CoIrO6 while preserving the symmetry of the lattices (P21/n) and the magnetism [Γ1(Ag)]. And more importantly, the magnitude of the symmetric distortion is correlated strongly with the size of the magnetic moment at temperatures below the Curie temperature (∼95 K). This strongly suggests a magnetoelastic coupling of the CBD mode. The order parameters for CBD, e.g., the movement of O1 toward Ir ions at low temperatures, are found to be in a linear-quadratic relationship with the value of the magnetic moment (∼0.002Å/μB2MCo2), manifesting the magnetoelastic CBD in double perovskite. © 2018 American Physical Societ

Soft ferromagnetism in mixed valence Sr1_ xLa xTi0.5Mn0.5O3 perovskites

The structural, magnetic and electrical properties of the mixed Ti–Mn oxides Sr1−xLaxTi0.5Mn0.5O3 (0 ≤ x ≤ 0.5) are reported. At room temperature the oxides have a cubic structure in space group Pmm for x ≤ 0.25 and rhombohedral in Rc for 0.3 ≤ x ≤ 0.50. X-ray absorption spectroscopic measurements demonstrate the addition of La3+ is compensated by the partial reduction of Mn4+ to Mn3+. Variable temperature neutron diffraction measurements show that cooling Sr0.6La0.4Ti0.5Mn0.5O3 results in a first order transition from rhombohedra to an orthorhombic structure in Imma. Complex magnetic behaviour is observed. The magnetic behaviour of the mixed valent (Mn3+/4+) examples is dominated by ferromagnetic interactions, although cation disorder frustrates long range magnetic orderin

High-Temperature Neutron and X‑ray Diffraction Study of Fast Sodium Transport in Alluaudite-type Sodium Iron Sulfate

Sodium-ion battery is a potential alternative to replace lithium-ion battery, the present main actor in electrical energy storage technologies. A recently discovered cathode material Na_2.5Fe_1.75(SO₄)₃ (NFS) derives not only high energy density with very high voltage generation over 3.8 V, but also high-rate capability of reversible Na insertion as a result of large tunnels in the alluaudite structure. Here we applied high-temperature X-ray/neutron diffraction to unveil characteristic structural features related to major Na transport pathways. Thermal activation and nuclear density distribution of Na demonstrate one-dimensional Na diffusion channels parallel to [001] direction in full consistence with computational predictions. This feature would be common for the related (sulfo-)­alluaudite system, forming emerging functional materials group for electrochemical applications