12 research outputs found
X-ray and neutron diffraction studies of coupled structural phase transitions in DyBaCoO
A structural transition at K from the to phase
is found to coincide with an anomaly of resistivity. Another structural phase
transition doubling the lattice parameter , which has been postulated
earlier to accompany a low-temperature magnetic transition in
TbBaCoO, is observed in a single crystal DbBaCoO by
means of the X-ray and neutron diffraction. The low temperature phase does not
belong to the space group that has been chosen earlier as the highest
subgroup of the . The transition is of the first order with the
temperature hysteresis, between and K, which
probably explains anomalous magnetic properties in this temperature range.Comment: 6 pages, 4 figure
Soft phonons and structural phase transition in superconducting Ba0.59K0.41BiO3
We have observed a softening of phonons and a structural phase transition in
a superconducting Ba0.59K0.41BiO3 (Tc = 31 K) single crystal using elastic and
inelastic neutron scattering measurements. The soft phonon occurs for the [111]
transverse acoustic mode at the zone boundary. The phonon energies in this
vicinity are found to continuously decrease with decreasing temperature from
above room temperature to 200 K, where a structural phase transition from cubic
to tetragonal symmetry occurs. The overall results are consistent with previous
data that reported phonon softening and a (0.5, 0.5, 0.5) type superstructure
in several Ba1-xKxBiO3 systems. However, we also find weak (0.5, 0.5, 0) type
superstructure peaks that reveal an additional component to the modulation. No
significant change related to the superconductivity was observed for the soft
phonon energies or linewidths.Comment: 15 page
Phonon Raman scattering in LaMn₁₋xCoxO₃ (x = 0, 0.2, 0.3, 0.4, and 1.0)
The Raman-active phonons in perovskite-like LaMn₁–xCoxO₃ (x = 0, 0.2, 0.3, 0.4, and 1.0) were studied by measuring Raman spectra at temperatures of 295 and 5 K. The changes in the spectra with Co doping are correlated with the decrease of orthorhombic distortions. Surprisingly more phonon lines than allowed for the rhombohedral LaCoO₃ structure were observed
Magnetic properties lithium-doped manganite single crystals
Magnetic and resistivity properties of La₁₋xLixMnO₃ single crystals with the perovskite structure at lithium concentrations x=0.06 and 0.2 are investigated over a broad temperature range at fields of up to 50 kOe. The Curie temperature is TC=90 K (x=0.06) and 300 K (x=0.2), respectively. The electrical resistance of the single crystal with x=0.06 increases steadily with temperature decrease, while the crystal with x=0.2 exhibits a magnetoresistance effect of ~ 8% at an external field of 9 kOe. The different dependence of the magnetizations MFC and MZFC of the sample with lower lithium content in the temperature range below TC is associated with the formation of a cluster glass and is caused by high coercivity and magnetic anisotropy of the crystal
Infrared transmission study of Pr 2 CuO 4 crystal-field excitations
PACS. 74.25.Gz Optical properties – 71.70.Ch Crystal and ligand fields – 74.72.Jt Other cuprates,
Magnetic Anisotropy in Geometrically Frustrated Kagome Staircase Lattices
This paper reviews experimental results concerning magnetic anisotropy in geometrically frustrated kagome staircase lattices. Following problems are discussed: high-temperature susceptibility measurements of kagome single crystals; inelastic neutron scattering measurements on Co3V2O8 single crystals; EPR of Co2+ ions in kagome staircase Mg3V2O8 single crystals. The single-ion anisotropy Hamiltonian is used to analyze experimental results. It is suggested that the magnetic anisotropy in kagome staircase M3V2O8 (M \ubc Co, Ni, Mn) oxides has mainly single-ion origin.Peer reviewed: YesNRC publication: Ye