Magnetic properties of ordered perovskites Ba₂LnTaO₆(Ln = Y, lanthanides)

Abstract

Magnetic properties of the quaternary oxides Ba2LnTaO6 (Ln = Y or lanthanides) are reported. Their powder x-ray diffraction measurements and Rietveld analysis show that they have an ordered perovskite structure and are monoclinic (Ln = La-Tb) with space group P21/n or cubic (Ln = Y, Dy-Lu) with space group Fm3̄m. Magnetic susceptibilities of Ba2LnTaO6 were measured. All compounds in this work are paramagnetic down to 5 K. Ba2EuTaO6 and Ba2SmTaO6 show Van Vleck paramagnetism; their spin-orbit coupling constants are determined to be 331 cm-1 and 287 cm-1, respectively. 151Eu Mössbauer measurements for Ba2EuTaO6 were carried out at 12, 100, 200 and 300 K. The Eu ion is in the trivalent state, and the symmetry of the Eu site is distorted from the octahedral symmetry. The Debye temperature of Eu3+ was determined to be 335 K from the temperature dependence of the absorption area of intensity curves.

Origin of colossal dielectric response in LaFeO3

“…where v AF H is the antiferromagnetic component, and r s is the saturation magnetization of the ferromagnetic component [24], which can be estimated by extrapolating the linear portion to zero field. r s is found to be 0.0197, 0.0193, 0.0187, 0.0181 and 0.0177 l B /f.u.…”

Raman-spectroscopic investigations on the crystal structure and phonon modes of Ba(RE1/2Ta1/2)O3 microwave ceramics

“…We found 24 non-degenerated Raman-active modes for both, orthorhombic Pbnm (D 16 2h ) and monoclinic P2 1 /n (C 5 2h ) structures, with the following reducible representations at the Brillouin zone centre (Wyckoff sites taken from Refs. 15,21 ): ortho = 7A g + 5B 1g + 7B 2g + 5B 3g + 8A u + 10B 1u + 8B 2u + 10B 3u and mono = 12A g + 12B g + 18A u + 18B u (all g = gerade modes are Raman active). If we were dealing with single crystalline samples, it would be quite simple to decide above the two groups above by using polarized Raman spectra, since the totally symmetric vibrations would be seen only in parallel polarizations and also cross-polarized spectra would be very different for different scattering symmetries.…”

“…However, the structure of these materials has been a matter of debate for many years, because X-ray structural data and vibrational-spectroscopic ones obtained by different authors are controversial. 10,[15][16][17][18][19][20][21] In a recent work, we have investigated the Raman phonon modes of several Ba(RE 1/2 Nb 1/2 )O 3 compounds, showing that tetragonal and orthorhombic structures were compatible with the observed features, with the phase transformation occurring with increasing ionic radius. 22 In this work, the evolution of the dielectric response and the structural changes of Ba(RE 1/2 Ta 1/2 )O 3 compounds are studied.…”

Crystal Structure and Magnetic Properties of 6H-Perovskite Ba3NdRu2O9

“…We consider that this transition temperature is exceptionally high, because it is known that the magnetic interaction between the f electrons is generally very weak compared with that between the d electrons, and because the main pathway of the magnetic exchange interaction between Nd ions is a long superexchange pathway of Nd}O}O}Nd. (19). Taking into account that the average valency of ruthenium ions is #4.5, there may exist Ru>Ru>O dimers.…”

“…The magnetic susceptibility shows a rapid increase when the temperature is decreased through 24 K, and the large divergence between the ZFC and FC susceptibilities is found below this temperature. These results indicate that a ferromagnetic or a ferrimagnetic transition has occurred at 24 K. We have already prepared analogous compounds Ba ¸n Ru O (¸n"Y, La, Lu) in which only Ru ions are magnetic, and we have measured their magnetic susceptibilities (19). They show antiferromagnetic transitions below 15 K. Hence, the Nd ions should contribute to the magnetic transition of (2) 8f 0.0037 (7) 0.3323 (7) (1) 2.023 (9) 2.021 (7) }O (2) 2.014 (8) 2.028 (7) }O (2) 2.042 (8) 2.051 (7) }O (3) 1.888 (8) 1.907 (7) }O (4) 1.931 (7) 1.946 (6) }O (5) 1.942 (7) 1.926(6) Ru}O (average) 1.973 (8) 1.980(7) Ru}Ru 2.542 (8) 2.522 (7) Ru}O (3) Ba NdRu O observed at 24 K. The temperature dependence of the inverse susceptibility (H/M) is shown in an inset graph in Fig.…”