Orbital order fluctuations in KCuF3

The interaction of orbital momenta of copper in KCuF3 via the field of elastic deformations is analyzed taking into account the local rotations of electron density on copper ions. It is found that the interaction energy related to local rotations of copper ions is comparable in order of magnitude with the Dzyaloshinskii-Moriya interaction energy. The calculated interaction energy of copper orbitals in the ab plane of the crystal exceeds the energy of their interaction along the c axis. This circumstance explains recently found specific features of orbital melting in LaMnO3 with increasing temperature. © 2014 Pleiades Publishing, Ltd

Crystal field theory and electric field gradients at 49Ti nuclei sites in LaTiO3

The energy level diagram and the wave functions for the Ti3+ ions (3d1) in LaTiO3 are calculated using modern crystal-field theory. The relative orbital ordering of these ions in the ground state is obtained. It turns out that the states of the ground triplet are considerably split and therefore the effect of the electronic-vibrational interaction is suppressed despite the fact that the distortions of the TiO 6 building block seem to be small. The components of the electric field gradient tensor at the Ti3+ nuclei sites are calculated using the wave functions of the ground states obtained. The calculated asymmetry parameter agrees well with the experimental values, which demonstrates the adequacy of the proposed orbital-ordering pattern of the Ti3+ ions in the ground state. © 2007 Pleiades Publishing, Ltd

Energy level diagram, wavefunctions, and probabilities of optical transitions in KCuF 3

Using modern concepts of the crystal field in ion-covalent compounds, we calculate the energy level diagram, wavefunctions, and probabilities of optical transitions in the orbital ordering phase of KCuF 3. On this basis, we discuss the possible mechanisms by which an optical absorption sideband structure forms, accompanied by the creation of magnons. © Pleiades Publishing, Ltd., 2011

Anisotropy of the paramagnetic susceptibility in LaTiO3_{3}: The electron-distribution picture in the ground state

The energy-level scheme and wave functions of the titanium ions in LaTiO$_{3}$ are calculated using crystal-field theory and spin-orbit coupling. The theoretically derived temperature dependence and anisotropy of the magnetic susceptibility agree well with experimental data obtained in an untwinned single crystal. The refined fitting procedure reveals an almost isotropic molecular field and a temperature dependence of the van Vleck susceptibility. The charge distribution of the 3d--electron on the Ti positions and the principle values of the quadrupole moments are derived and agree with NMR data and recent measurements of orbital momentum $$ and crystal-field splitting. The low value of the ordered moment in the antiferromagnetic phase is discussed.Comment: 6 pages, 2 figures, 3 table

Optical evidence for symmetry changes above the Neel temperature in KCuF3

We report on optical measurements of the 1D Heisenberg antiferromagnet KCuF3. The crystal-field excitations of the Cu2+ ions have been observed and their temperature dependence can be understood in terms of magnetic and exchange-induced dipole mechanisms and vibronic interactions. Above T_N we observe a new temperature scale T_S characterized by the emergence of narrow absorption features that correlate with changes of the orbital ordering as observed by Paolasini et al. [Phys. Rev. Lett. 88, 106403 (2002)]. The appearance of these optical transitions provides evidence for a symmetry change above the Neel temperature that affects the orbital ordering and paves the way for the antiferromagnetic ordering.Comment: 4 pages, 2 figure

Optical evidence for symmetry changes above the Néel temperature of KCuF3

We report on optical measurements of the 1D Heisenberg antiferromagnet KCuF3. The crystal-field excitations of the Cu2+ ions have been observed and their temperature dependence can be understood in terms of magnetic and exchange-induced dipole mechanisms and vibronic interactions. Above TN we observe a new temperature scale TS characterized by the emergence of narrow absorption features that correlate with changes of the orbital ordering as observed by Paolasini et al.. The appearance of these optical transitions provides evidence for a symmetry change above the Néel temperature that affects the orbital ordering and paves the way for the antiferromagnetic ordering. © 2008 The American Physical Society

Anisotropy paramagnetic susceptibility in LaTiO3

The energy-level scheme and wave functions of titanium ions in LaTiO 3 are calculated using crystal-field theory. The theoretically derived temperature dependence of the magnetic susceptibility agrees with our new experimental data obtained in an untwinned single crystal

Anisotropy of the paramagnetic susceptibility in LaTiO3: The electron-distribution picture in the ground state

The energy-level scheme and wave functions of the titanium ions in LaTiO3 are calculated using crystal-field theory and spin-orbit coupling. The theoretically derived temperature dependence and anisotropy of the magnetic susceptibility agree well with experimental data obtained in an untwinned single crystal. The refined fitting procedure reveals an almost isotropic molecular field and a temperature dependence of the van Vleck susceptibility. The charge distribution of the 3d-electron on the Ti positions and the principle values of the quadrupole moments are derived and agree with NMR data and recent measurements of orbital momentum 〈l〉 and crystal-field splitting. The low value of the ordered moment in the antiferromagnetic phase is discussed

Orbital order fluctuations in KCuF3

The interaction of orbital momenta of copper in KCuF3 via the field of elastic deformations is analyzed taking into account the local rotations of electron density on copper ions. It is found that the interaction energy related to local rotations of copper ions is comparable in order of magnitude with the Dzyaloshinskii-Moriya interaction energy. The calculated interaction energy of copper orbitals in the ab plane of the crystal exceeds the energy of their interaction along the c axis. This circumstance explains recently found specific features of orbital melting in LaMnO3 with increasing temperature. © 2014 Pleiades Publishing, Ltd

Orbital order fluctuations in KCuF3

The interaction of orbital momenta of copper in KCuF3 via the field of elastic deformations is analyzed taking into account the local rotations of electron density on copper ions. It is found that the interaction energy related to local rotations of copper ions is comparable in order of magnitude with the Dzyaloshinskii-Moriya interaction energy. The calculated interaction energy of copper orbitals in the ab plane of the crystal exceeds the energy of their interaction along the c axis. This circumstance explains recently found specific features of orbital melting in LaMnO3 with increasing temperature. © 2014 Pleiades Publishing, Ltd