Neutron diffraction studies and the magnetism of an ordered perovskite: Ba2CoTeO6

Abstract

The complex perovskite Ba(2)CoTeO(6) (BCTO) has been synthesised, and the crystal structure and magnetic properties have been investigated using a combination of X-ray and neutron powder diffraction, electron microscopy and dielectric, calorimetric and magnetic measurements. It is shown that at room temperature this compound adopts the 6L-trigonal perovskite structure, space group P3[combining macron]m (s.g. 164) (a = 5.7996(1) A, c = 14.2658(3) A). The structure comprises dimers of face-sharing octahedra as well as octahedra which share only vertices with their neighbours. Dielectric measurements indicate a diffuse transition of antiferroelectric nature near 280 K. A long-range antiferromagnetically ordered state has been identified from neutron diffraction and magnetic studies. The magnetic diffraction peaks were registered below the magnetic transition at about 15 K and a possible model for the magnetic structure is proposed. The structural and magnetic features of this compound are discussed and compared with those of other Co-based quaternary oxides adopting the perovskite structure.

Synthesis and characterisation of the vibrational and electrical properties of antiferromagnetic 6L-Ba2CoTeO6ceramics

“…Some ordering between the B-site cations was proposed. This structural determination was further corroborated by neutron diffraction analysis carried out by Ivanov et al, 15 who also showed the absence of any structural transitions between 5 and 295 K. Ba 2 CrMoO 6 , 16 Ba 2 CoOsO 6 , and Ba 2 NiOsO 6 17 are other compounds that were also reported to adopt the 6-layered BaTiO 3 -type structure.…”

“…Although BCTO was claimed to be antiferroelectric, the necessary evidence in the form of a polarisation vs. electric field (P-E) double loop 19 data was not provided. In 2010, Ivanov et al 15 also commented on the absence of a P-E hysteresis loop up to the breakdown field of BCTO ceramics.…”

Field-driven successive phase transitions in the quasi-two-dimensional frustrated antiferromagnetBa2CoTeO6and highly degenerate classical ground states

“…With increasing magnetic field, T N1 for H c shifts toward the low-temperature side, which is more clearly observed in specific heat data shown below. For H ⊥ c, the bend anomaly at T N2 observed below 5 T changes into a cusp anomaly above 6 T. Figure 4 shows the temperature dependence of the specific heat divided by temperature, C/T , below 16 K measured at various magnetic fields for H c and H ⊥ c. At zero magnetic field, two sharp peaks indicative of magnetic phase transitions are observed at T N1 = 11.93 and T N2 = 2.91 K. T N1 is somewhat lower than T N ≃ 15 K reported by Ivanov et al [23]. For H c, T N1 shifts toward the low-temperature side with increasing magnetic field, whereas T N2 is almost independent of the magnetic field.…”

Structural phase transitions and magnetic and spectroscopic properties of the double perovskites Sr2Co1−xMgxTeO6(x = 0.1, 0.2 and 0.5)

“…Oxides of this type have received much attention in recent years due to the observation of properties with high application potential such as the large magnetoresistance and room temperature half metallicity observed in Sr 2 FeMoO 6 and related oxides, 1,2 high ionic conductivity in Sr 2 Mg 1−x -Mn x MoO 6−δ 3 or the coexistence of ferroelectricity and ferromagnetism (multiferroic behavior) in Bi 2 NiMnO 6 4 and La 2 NiMnO 6 . 9 The latter compounds show interesting structural changes when the A-site cation is changed (from conventional perovskite phases if A is small to hexagonal modifications if it is very large as in the case of Ba 2+ ions 10 ) and also when the temperature is changed (if A = Sr 11 or Pb, 12 so far). The study of cobalt containing double perovskites with the formula A 2 CoB′O 6 has gained interest in recent years.…”