On the Structural and Electronic Factors Governing the Magnetic Properties of the Hexagonal Perovskite-Type Oxides A x BO 3 ( A=Ca, Sr, Ba; B=Co, Ni (original) (raw)
Related papers
Structural Chemistry and Magnetic Properties of the BaMn 0.4 Co 0.6 O 2.83 Hexagonal Perovskite
Chemistry of Materials, 2007
The complete structural characterization of the hexagonal cobaltite BaMn 0.4 Co 0.6 O 2.83 has been performed by combining high-resolution transmission electron microscopy and electron and neutron diffraction. The structure is closely related to the 12H (cc′chhh) 2 with oxygen deficient cubic c′-BaO 2 layers. This framework forms a laminar structure in which tetramers of face-sharing octahedra occupied by manganese and cobalt are connected by corners to two tetrahedral layers mostly occupied by cobalt. A magnetic study shows only the presence of short-range magnetic interactions indicating that there are no interactions between the tetramers through the tetrahedral layers, thus impeding the three-dimensional magnetic ordering of the system. A spin-glass-like state was found to be compatible with the observed phenomenology. 91 394 43 52.
Synthesis, crystal structure, and magnetic properties of new layered hexagonal perovskite Ba8Ta4Ru8/3Co2/3O24
A new hexagonal perovskite-type oxide Ba8Ta4Ru8/3Co2/3O24 was synthesized by the solid-state method at 1573K and characterized by electron diffraction (ED), time-of-flight (TOF) neutron powder diffraction, and magnetic susceptibility. Structure parameters of Ba8Ta4Ru8/3Co2/3O24 were refined by the Rietveld method from the TOF neutron powder diffraction data on the basis of space group P63=mcm and lattice parameters a ¼ 10:0075ð1ÞA ˚ and c ¼ 18:9248ð2ÞA ˚ as obtained from the ED data (Z ¼ 3). The crystal structure of Ba8Ta4Ru8/3Co2/3O24 consists of 8-layered (cchc)2 close-packed stackingof BaO3 layers alongthe c-axis. Corner-shared octahedra are filled by Ta only and face-shared octahedra are statistically occupied by Ru, Co, and vacancies. Similar compounds Ba8Ta4Ru8/3M2/3O24 with M=Ni and Zn were also prepared. Magnetic susceptibility measurements showed no magnetic ordering down to 5K.
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.
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.
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.
Possible spin configurations and magnetism inBaCoO3 perovskite
International Journal of Quantum Chemistry, 2003
The electronic structure, spin densities, and band structure of the perovskite BaCoO3 have been obtained using the spin-polarized density functional theory within the generalized-gradient approximation and the full-potential linearized augmented plane wave method, adding local orbitals to the basis set. Different spin configurations were estimated using the fixed-spin–moment method. The ground state that results after a partial geometry optimization to reduce the internal forces on the structure is magnetic with the Co ions in a low-spin state. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2003
Magnetic ground state of the distorted 6H perovskite Ba3CdIr2O9
Physical Review B, 2019
Perovskite iridates of 6H hexagonal structure present a plethora of possibilities in terms of the variety of ground states resulting from a competition between spin-orbit coupling (SOC), hopping, noncubic crystal field (∆ NC CFE) and superexchange energy scales within the Ir 2 O 9 dimers. Here we have investigated one such compound Ba 3 CdIr 2 O 9 by x-ray diffraction, dc magnetic susceptibility(χ), heat capacity(C p) and also 113 Cd nuclear magnetic resonance (NMR) spectroscopy. We have established that the magnetic ground state has a small but finite magnetic moment on Ir 5+ in this system, which likely arises from intradimer Ir-Ir hopping and local crystal distortions. Our heat capacity, NMR, and dc magnetic susceptibility measurements further rule out any kind of magnetic long-/short range ordering among the Ir moments down to at least 2K. In addition, the magnetic heat capacity data shows linear temperature dependence at low temperatures under applied high fields (> 30 kOe), suggesting gapless spin-density of states in the compound.
Inorganic Chemistry, 2002
Based on the density functional theory (DFT), the full-potential linearized augmented plane wave with local orbital (FP-L/APW+ lo) technique is now employed in this approach to understand the structural, electronic, and magnetic properties of simple cubic oxide perovskite NdGaO 3 compound. In all this investigation, the exchange-correlation (XC) energy is selected in the framework of spin-polarized generalized gradient approximation (spin-GGA). The structural analysis unveils that the ferromagnetic (FM) phase is the stable ground state of the cubic NdGaO 3 compound, where the equilibrium lattice parameters (lattice constant (a 0), bulk modulus (B 0), and its first pressure derivative (B′)) are determined in both FM and paramagnetic (PM) phases. The spinpolarized electronic properties (band structure and density of states) of the cubic NdGaO 3 oxide perovskite are studied under the platform of equilibrium lattice parameters; this investigation demonstrates the half-metallic behavior of the studied cubic NdGaO 3 compound because the spin-up case displays the metallic nature, whereas the semiconducting character is observed in spin-down case. The magnetic properties reveal that the total magnetic moment of the cubic NdGaO 3 compound is equal to 3 μ B and its contribution is mostly generated by Nd atoms, whereas feeble local magnetic moments are installed in non-magnetic Ga and O sites. Through the electronic and magnetic results, we conclude that the cubic perovskite NdGaO 3 compound is classified as a half-metallic ferromagnetic material.
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.