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The crystal structure of La x Sr 1-x MnO (5+x)/2 was analyzed from the powder diffraction data and Rietveld method. The specimen was prepared by the solid-state reaction method under low oxygen partial pressure. The results of the structural analysis showed several different structures which were modified from perovskite type with ordered arrangement of oxygen vacancies, depending on the composition. La 0.1 Sr 0.9 MnO 2.55 had orthorhombic structure (Pbam) with the lattice dimension of √2a p x 2√2a p x 1a p . La 0.2 Sr 0.8 MnO 2.60 and La 0.3 Sr 0.7 MnO 2.65 had a monoclinic structure (P2/m) with the lattice dimension of √5a p x 1a p x √5a p . La 0.4 Sr 0.6 MnO 2.70 had a cubic cell (Pm3m) with the lattice dimension of 1a p x 1a p x 1a p . La 0.5 Sr 0.5 MnO 2.75 had a tetragonal structure (I4/mmm) with the lattice dimension of √2a p x √2a p x 2a p .

The La-substituted manganites (La x Sr 1− x MnO 3 ) in La poor side were studied by means of X-ray diffraction. The La-poor side for La x Sr 1− x MnO 3 (0≤ x ≤0.1) transformed at high temperature. La x Sr 1− x MnO 3 have cubic perovskite structure, but at high temperature, each perovskite structure transformed into layer structure. La 0.025 Sr 0.975 MnO 3 , La 0.05 Sr 0.95 MnO 3 and La 0.1 Sr 0.9 MnO 3 transformed to 4-layer structure, 15-layer structure and 6-layer structure, respectively.

The oxygen defect perovskite La x Sr 1− x MnO (5+ x )/2 phases ( x =0.8–1.0) with valence state adjusted to trivalent manganese ion have been prepared by reducing oxygen content from the series of La x Sr 1− x MnO 3 solid solutions. These phases have been characterized by powder X-ray diffractometry and magnetization measurement. The crystal systems of La x Sr 1− x MnO (5+ x )/2 are orthorhombic ( x =1.0–0.9) and rhombohedral ( x =0.8). The phase of La x Sr 1− x MnO 3+ δ for x =0.9 shows structural change from rhombohedral to orthorhombic symmetry by degree of oxygen nonstoichiometry, while the compounds for x =1.0 and 0.8 do not show structural change by oxygen nonstoichiometry. The random distribution of the oxygen vacancies are assumed in each structure. For x =0.8, the behavior of the temperature dependence of gram magnetization is quite different for finite-field cooling and for zero-field cooling, whereas the magnetic transition temperature exists at around 138 K for both cases. It seems that the magnetic ordered state of this sample is weak ferromagnetic.

A perovskite compound La 2 MnRuO 6 was synthesized and the detailed crystal structure has been determined by Rietveld analysis of powder X-ray diffraction data. The nonstoichiometric range of La 2 MnRuO 6+ x phase was determined from x =−0.015 to +0.152. The lattice constants with the orthorhombic space group Pnma (No 62) decrease with increase of oxygen nonstoichiometry from a =0.56921(8), b =0.78354(3) and c =0.55513(7) nm near stoichiometric composition to a =0.55594(2), b =0.78309(3) and c =0.55484(2) nm for hyperstoichiometric composition. The oxygen octahedron is almost regular and tilts each other in zigzag way by several degrees. The magnetic measurements of this phase showed a spin glass like behavior with a characteristic peak phenomenon below 100 K in the susceptibility–temperature curve ( χ – T ) at low temperature.

The crystal and magnetic structure of SrMnO 2.5 has been investigated by neutron power diffraction from 20 to 425 K. The compound has orthorhombic crystal structure with the unit cell dimensions a =0.55307(4), b =1.07829(8), c =0.38145(3) nm at 425 K, where space group is Pbam and Z =4. Below T N =375 K, an antiferromagnetic order occurs and the magnetic unit cell is orthorhombic with the dimensions a m = a c , b m = b c , c m =2 c c , where a c , b c and c c are the parameters of the crystallographic unit cell. The ferromagnetic and antiferromagnetic coupling coexist in the c-plane according to the difference of Mn–O–Mn angle and the coupling between adjacent planes is antiferromagnetic. The direction of the magnetic moments is along the crystallographic b-axis. The magnitude of magnetic moment at 20 K is 3.44 μ B /Mn.