Magnetic properties of the 6H perovskite Ba_{3}Fe_{2}TeO_{9}$ (original) (raw)
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Crystal structure and magnetism of the double perovskites A 2 FeReO 6 (A= Ca, Sr, Ba)
double perovskites have been prepared in polycrystalline form by solid state reaction, in air. These materials have been studied by X-ray diffraction (XRD), neutron powder diffraction (NPD) and magnetic measurements. At room temperature, the crystal structure of Sr 3 Fe 2 TeO 9 is tetragonal, space group I4/m, with a = b = 5.55902(4) Å , c = 7.885(1) Å , whereas Ba 3 Fe 2 TeO 9 presents a hexagonal lattice, space group P6 3 /mmc, with a = 5.7670(1) Å , c = 14.1998(4) Å . The structure of Sr 3 Fe 2 TeO 9 , which can ideally be rewritten as Sr 2 Fe(Fe 1/3 Te 2/3 )O 6 , can be described as the result of a single anti-phase tilting of the FeO 6 and (Fe,Te)O 6 octahedra along the c axis, exhibiting a tilting angle of 4.5u at RT. Ba 3 Fe 2 TeO 9 shows a different stacking of the Fe/Te octahedra: the structure is constituted by dimer units of (Fe,Te)O 6 octahedra sharing a face along the c axis; the dimers are connected, sharing corners, by a single layer of FeO 6 octahedra. In both Sr and Ba compounds a certain degree of antisite disordering has been detected, implying the presence of about 15% Te at Fe positions. Magnetic measurements show the onset of ferrimagnetic ordering at relatively high temperatures of 717 and 711 K for the Sr and Ba compounds, respectively; however the magnetization isotherms at 2 K exhibit, for H = 50 kOe, maximum magnetization values close to 0.8 m B f.u. 21 and 0.35 m B f.u. 21 for Sr and Ba compounds respectively, although full saturation is not reached. The extremely weak magnetic scattering contribution observed on the low-temperature NPD patterns for Sr 3 Fe 2 TeO 9 is in contrast with the well-established ferrimagnetic structures observed for other members of the Sr 3 Fe 2 B0O 9 double perovskite series (B0 = U, Mo, W). This distinct behavior is discussed as a function of the chemical nature of the different B0 hexavalent cations.
Novel anion-deficient perovskite-based ferrites Pb2Ba2BiFe5O13 and Pb1.5Ba2.5Bi2Fe6O16 were synthesized by solid-state reaction in air. Pb2Ba2BiFe5O13 and Pb1.5Ba2.5Bi2Fe6O16 belong to the perovskite-based AnBnO3n−2 homologous series with n = 5 and 6, respectively, with a unit cell related to the perovskite subcell ap as ap√2 × ap × nap√2. Their structures are derived from the perovskite one by slicing it with 1/ 2[110]p(1̅01)p crystallographic shear (CS) planes. The CS operation results in (1̅01)pshaped perovskite blocks with a thickness of (n − 2) FeO6 octahedra connected to each other through double chains of edge-sharing FeO5 distorted tetragonal pyramids which can adopt two distinct mirror-related configurations. Ordering of chains with a different configuration provides an extra level of structure complexity. Above T ≈ 750 K for Pb2Ba2BiFe5O13 and T ≈ 400 K for Pb1.5Ba2.5Bi2Fe6O16 the chains have a disordered arrangement. On cooling, a second-order structural phase transition to the ordered state occurs in both compounds. Symmetry changes upon phase transition are analyzed using a combination of superspace crystallography and group theory approach. Correlations between the chain ordering pattern and octahedral tilting in the perovskite blocks are discussed. Pb2Ba2BiFe5O13 and Pb1.5Ba2.5Bi2Fe6O16 undergo a transition into an antiferromagnetically (AFM) ordered state, which is characterized by a G-type AFM ordering of the Fe magnetic moments within the perovskite blocks. The AFM perovskite blocks are stacked along the CS planes producing alternating FM and AFM-aligned Fe−Fe pairs. In spite of the apparent frustration of the magnetic coupling between the perovskite blocks, all n = 4, 5, 6 AnFenO3n−2 (A = Pb, Bi, Ba) feature robust antiferromagnetism with similar Néel temperatures of 623−632 K.
European Journal of Inorganic Chemistry, 2008
Ba 2 MSbO 6-δ (M = Fe, Co) double perovskites have been prepared in polycrystalline form by the solid-state reaction in air and characterized by X-ray diffraction (XRD), neutron powder diffraction (NPD), magnetic measurements and Mössbauer spectroscopy (for M = Fe). At room temperature, the crystal structure of both compounds can be defined as a 6layered (6H) hexagonal perovskite structure (space group P6 3 /mmc), with a = 5.7875(1) Å and c = 14.2104(2) Å for M = Fe and a = 5.7548(2) Å and c = 14.1439(7) Å for M = Co. M and Sb cations are randomly distributed over 4f and 2a Wickoff positions. The crystal structure is constituted by dimer units of (M,Sb) 4f O 6 octahedra sharing a face along the c axis; the dimers, which sharing corners, are connected by a single layer of (M,Sb) 2a O 6 octahedra. A severe degree of antisite disordering was detected in the Fe compound, which indicates the presence of 52.8 % Fe:47.2 % Sb at the (Fe,Sb) 2a positions, whereas for Co, 64.0 % Sb is present at the (Co,Sb) 2a sites. Mössbauer spectroscopic data for Ba 2 FeSbO 6
Magnetic properties of ordered Perovskite Ba2FeMoO6
Journal of Magnetism and Magnetic Materials, 2003
Magnetic properties have been investigated for ordered perovskite Ba 2 FeMoO 6. Saturation magnetization is 3.7 m B / f.u. which is consistent with the Fe/Mo ordering of 97% estimated from X-ray refinement. Magnetization could be interpreted as a mixture of ferromagnetic and paramagnetic components. The paramagnetic component has been found to increase substantially with increasing temperature from 21% at 20 K to 55% at room temperature.
Evolution of the structural, magnetic, and electronic properties of the triple perovskite Ba3CoIr2O9
Physical Review B, 2021
We report a comprehensive investigation of the triple perovskite iridate Ba3CoIr2O9. Stabilizing in the hexagonal P 63/mmc symmetry at room temperature, this system transforms to a monoclinic C2/c symmetry at the magnetic phase transition. On further reduction in temperature, the system partially distorts to an even lower symmetry (P 2/c), with both these structurally disparate phases coexisting down to the lowest measured temperatures. The magnetic structure as determined from neutron diffraction data indicates a weakly canted antiferromagnetic structure, which is also supported by first-principles calculations. Theory indicates that the Ir 5+ carries a finite magnetic moment, which is also consistent with the neutron data. This suggests that the putative J = 0 state is avoided. Measurements of heat capacity, electrical resistance noise and dielectric susceptibility all point towards the stabilization of a highly correlated ground state in the Ba3CoIr2O9 system.
Chemistry of Materials, 2017
Double perovskite oxides A2BB'O6 combining 3d and 4d or 5d transition metal ions at the B and B' sites feature a variety of magnetic and magneto-electric properties. Targeting Ba2FeOsO6 we synthesized powder samples of non-stoichiometric Ba2Fe1.12Os0.88O6 by solidstate reaction from the oxides. The crystal structure was investigated by using synchrotron powder x-ray and powder neutron diffraction. In contrast to Ca2FeOsO6 and Sr2FeOsO6, the compound adopts the hexagonal 6L perovskite structure (space group 1 3m P) with partial Fe-Os order at both the edge-sharing B2O9 dimer and the corner sharing BO6 transition metal sites. Magnetization, neutron diffraction, and 57 Fe Mössbauer spectroscopy results show that Ba2Fe1.12Os0.88O6 develops ferrimagnetic order well above room temperature at TC ~ 370 K. The non-saturated magnetization curve at 2 K features a magnetic moment of 0.4 µB per formula unit at 7 T and a pronounced hysteresis with a coercive field of about 2 T. Large exchange bias effects are observed when the magnetization curves are measured after field cooling. The peculiar magnetic properties of Ba2Fe1.12Os0.88O6 are attributed to an inhomogeneous magnetic state formed as a consequence of the atomic disorder. Our results indicate that hexagonal double-perovskite-related oxides are a promising class of compounds for finding new materials with potential applications as hard magnets or in the area of spintronics.
Crystal Structure and Magnetic Properties of 6H-Perovskite Ba3NdRu2O9
Journal of Solid State Chemistry, 2001
Magnetic properties of a quaternary oxide Ba 3 NdRu 2 O 9 are reported. This compound adopts the 6H-perovskite structure with space group P6 3 /mmc, in which the cation sites within the face-sharing octahedra are occupied by ruthenium ions and those within the corner-sharing octahedra are occupied by neodymium ions. Powder neutron di4raction, powder X-ray di4raction, magnetic susceptibility, magnetization, and speci5c heat measurements were carried out. It was found that the crystal phase transition and magnetic transition occurred at ca. 120 K and 24 K, respectively. The crystal structure below 120 K is monoclinic with space group C 2/c. Neutron di4raction data collected at 10 K show that Ba 3 NdRu 2 O 9 has a long-range ferromagnetic ordering of Nd 3؉ ions. The ordered magnetic moment of Nd 3؉ ions is 1.65(8) B . The direction of ordered moments is parallel to the c-axis.
Azad_Preparation,-crystal-and-magnetic-structure-of-the-double-perovskite-Ba2FeWO6_2002.pdf
Single-phase polycrystalline material of the double perovskite Ba 2 FeWO 6 was prepared and characterized by X-ray and neutron powder diffraction (NPD). The crystal structure was tetragonal with lattice parameters a = b = 5.7479(4) Å and c = 8.1444(9) Å at room temperature (295 K). NPD data at 10 K shows the evidence of an antiferromagnetic ordering of the Fe atoms. The reverse Monte Carlo powder (RMCPOW) technique was used to find the magnetic structure, which showed that it is based on a unit cell related to that of the nuclear structure by the propagation vector 0 1 2 1 2 . An ordering of collinear spins was found with alternate layers in the c-direction or in the a − b plane. The model was checked by Rietveld refinement and the magnetic moment of iron was found to be 3.39(2)µ B at 10 K.
Journal of Alloys and Compounds, 2009
The crystallographic and magnetic structures of polycrystalline Ba 2 (Fe,W) 2 O 6 and Ba 2 (Fe,W 0.5 Mo 0.5 ) 2 O 6 double-perovskites have been investigated by X-ray and neutron powder diffraction (NPD), magnetization and Mössbauer spectroscopy. The samples were synthesized by conventional solid-state reaction at temperatures about 1273 K. The compounds crystallize in the cubic structure with space group Fm3m. The magnetic structures were determined by neutron powder diffraction between 5 K and 310 K. Evidence for an antiferromagnetic behavior has been observed for Ba 2 (Fe,W) 2 O 6 with T N = 24.7 K and a two-phase separation for Ba 2 (Fe,W 0.5 Mo 0.5 ) 2 O 6 into an antiferromagnetic structure of the W-type with T N = 24.7 K and the ferromagnetic Mo-type with T C = 270 K.
Structural and Magnetic Investigation of the Double-Perovskite Ba2Co1−x Fe x ReO6 (0 ≤ x ≤ 0.5)
Journal of Superconductivity and Novel Magnetism, 2015
Double-perovskite series of Ba 2 Co 1−x Fe x ReO 6 (x = 0, 0.2, 0.4, and 0.5) were prepared as singlephase materials using the conventional solid-state reaction method and studied by X-ray powder diffraction and magnetization techniques. The Rietveld analysis of the X-ray diffraction patterns showed a partial disordering in the Re and Fe/Co layers on the B sites of the double perovskites, which played a central role in the structural and magnetic properties of the compounds. The findings showed that symmetry was cubic (Fm3m) for all of the samples. The magnetization versus temperature measurements at H = 500 Oe revealed that the Ba 2 CoReO 6 and Ba 2 Co 0.8 Fe 0.2 ReO 6 samples showed antiferromagnetic state and exhibited a paramagnetic-ferromagnetic transition for x = 0.4 and 0.5. The Curie temperature was also noted to increase with the increase in the Fe content.