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Kh E Elkelany - One of the best experts on this subject based on the ideXlab platform.
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spin localization Magnetic Ordering and electronic properties of strongly correlated ln 2 o 3 sesquioxides ln la ce pr nd
Physical Review B, 2018Co-Authors: Kh E Elkelany, Corentin Ravoux, Jacques K Desmarais, Pietro Cortona, Yuanming Pan, John S Tse, Alessandro ErbaAbstract:Lanthanide sesquioxides are strongly correlated materials characterized by highly localized unpaired electrons in the f band. Theoretical descriptions based on standard density functional theory (DFT) formulations are known to be unable to correctly describe their peculiar electronic and Magnetic features. In this study, electronic and Magnetic properties of the first four lanthanide sesquioxides in the series are characterized through a reliable description of spin localization as ensured by hybrid functionals of the DFT, which include a fraction of nonlocal Fock exchange. Because of the high localization of the f electrons, multiple metastable electronic configurations are possible for their ground state depending on the specific partial occupation of the f orbitals: the most stable configuration is here found and characterized for all systems. Magnetic Ordering is explicitly investigated, and the higher stability of an antiferroMagnetic configuration with respect to the ferroMagnetic one is predicted. The critical role of the fraction of exchange on the description of their electronic properties (notably, on spin localization and on the electronic band gap) is addressed. In particular, a recently proposed theoretical approach based on a self-consistent definition—through the material dielectric response—of the optimal fraction of exchange in hybrid functionals is applied to these strongly correlated materials.
T Inami - One of the best experts on this subject based on the ideXlab platform.
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Magnetic Ordering and spin dynamics in potassium jarosite a heisenberg kagome lattice antiferromagnet
Physical Review B, 2003Co-Authors: Masahide Nishiyama, S Maegawa, T InamiAbstract:The spin dynamics of the Heisenberg kagom\'e lattice antiferromagnet, potassium jarosite ${\mathrm{KFe}}_{3}(\mathrm{OH}{)}_{6}({\mathrm{SO}}_{4}{)}_{2},$ have been investigated by means of NMR. The NMR spectra confirm the long-range Magnetic Ordering below 65 K and the $\mathbf{q}=0$ type $120\ifmmode^\circ\else\textdegree\fi{}$ spin structure with positive chirality in the ordered phase. Though the Heisenberg kagom\'e lattice antiferromagnet is considered theoretically to remain disordered down to zero temperature due to the continuous degeneracy of the ground state, the long-range Magnetic Ordering at the finite temperature is realized in this compound due to the weak anisotropy. The spin-lattice relaxation rate, ${1/T}_{1},$ in the ordered phase decreases sharply with lowering temperature. The experimental rate is well explained by the two-magnon process of the spin waves having an energy gap of 15 K. The temperature dependence of the sublattice magnetization also supports the existence of the spin wave. These are the first experimental evidence that the low-energy excitation in the frustrated classical kagom\'e lattice antiferromagnet is described by the spin wave. We calculate the spin wave in the $\mathbf{q}=0$ type $120\ifmmode^\circ\else\textdegree\fi{}$ spin structure with weak single-ion-type anisotropy, and discuss the characteristics of the spin fluctuations in the Heisenberg kagom\'e lattice antiferromagnet.
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Magnetic structure of the kagome lattice antiferromagnet potassium jarosite kfe 3 oh 6 s o 4 2
Physical Review B, 2000Co-Authors: T Inami, Masahide Nishiyama, S MaegawaAbstract:We have examined the Magnetic structure of the kagom\'e lattice antiferromagnet potassium jarosite (K jarosite: ${\mathrm{KFe}}_{3}{(\mathrm{OH})}_{6}{(\mathrm{S}\mathrm{O}}_{4}{)}_{2})$ by means of powder neutron diffraction. Extremely high degeneracy of the ground states prevents the long-range Magnetic Ordering at any temperature and the $\sqrt{3}\ifmmode\times\else\texttimes\fi{}\sqrt{3}$ structure is predicted theoretically to be favored rather than the $q=0$ structure at $T=0$ in a kagom\'e lattice Heisenberg antiferromagnet. Nevertheless, K jarosite shows long-range Magnetic Ordering at 65 K and the ordered Magnetic structure was found to be the $q=0$ structure. In addition, although the $q=0$ structure has two degenerated states of ``positive'' and ``negative'' chirality, the observed Magnetic structure contains only elemental triangles of positive chirality. We found that a weak single-ion-type anisotropy is crucial for selecting the observed Magnetic structure. The long-range Magnetic Ordering at finite temperature in the jarosite family of compounds can be ascribed to this anisotropy.
Alessandro Erba - One of the best experts on this subject based on the ideXlab platform.
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spin localization Magnetic Ordering and electronic properties of strongly correlated ln 2 o 3 sesquioxides ln la ce pr nd
Physical Review B, 2018Co-Authors: Kh E Elkelany, Corentin Ravoux, Jacques K Desmarais, Pietro Cortona, Yuanming Pan, John S Tse, Alessandro ErbaAbstract:Lanthanide sesquioxides are strongly correlated materials characterized by highly localized unpaired electrons in the f band. Theoretical descriptions based on standard density functional theory (DFT) formulations are known to be unable to correctly describe their peculiar electronic and Magnetic features. In this study, electronic and Magnetic properties of the first four lanthanide sesquioxides in the series are characterized through a reliable description of spin localization as ensured by hybrid functionals of the DFT, which include a fraction of nonlocal Fock exchange. Because of the high localization of the f electrons, multiple metastable electronic configurations are possible for their ground state depending on the specific partial occupation of the f orbitals: the most stable configuration is here found and characterized for all systems. Magnetic Ordering is explicitly investigated, and the higher stability of an antiferroMagnetic configuration with respect to the ferroMagnetic one is predicted. The critical role of the fraction of exchange on the description of their electronic properties (notably, on spin localization and on the electronic band gap) is addressed. In particular, a recently proposed theoretical approach based on a self-consistent definition—through the material dielectric response—of the optimal fraction of exchange in hybrid functionals is applied to these strongly correlated materials.
S Maegawa - One of the best experts on this subject based on the ideXlab platform.
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Magnetic Ordering and spin dynamics in potassium jarosite a heisenberg kagome lattice antiferromagnet
Physical Review B, 2003Co-Authors: Masahide Nishiyama, S Maegawa, T InamiAbstract:The spin dynamics of the Heisenberg kagom\'e lattice antiferromagnet, potassium jarosite ${\mathrm{KFe}}_{3}(\mathrm{OH}{)}_{6}({\mathrm{SO}}_{4}{)}_{2},$ have been investigated by means of NMR. The NMR spectra confirm the long-range Magnetic Ordering below 65 K and the $\mathbf{q}=0$ type $120\ifmmode^\circ\else\textdegree\fi{}$ spin structure with positive chirality in the ordered phase. Though the Heisenberg kagom\'e lattice antiferromagnet is considered theoretically to remain disordered down to zero temperature due to the continuous degeneracy of the ground state, the long-range Magnetic Ordering at the finite temperature is realized in this compound due to the weak anisotropy. The spin-lattice relaxation rate, ${1/T}_{1},$ in the ordered phase decreases sharply with lowering temperature. The experimental rate is well explained by the two-magnon process of the spin waves having an energy gap of 15 K. The temperature dependence of the sublattice magnetization also supports the existence of the spin wave. These are the first experimental evidence that the low-energy excitation in the frustrated classical kagom\'e lattice antiferromagnet is described by the spin wave. We calculate the spin wave in the $\mathbf{q}=0$ type $120\ifmmode^\circ\else\textdegree\fi{}$ spin structure with weak single-ion-type anisotropy, and discuss the characteristics of the spin fluctuations in the Heisenberg kagom\'e lattice antiferromagnet.
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Magnetic structure of the kagome lattice antiferromagnet potassium jarosite kfe 3 oh 6 s o 4 2
Physical Review B, 2000Co-Authors: T Inami, Masahide Nishiyama, S MaegawaAbstract:We have examined the Magnetic structure of the kagom\'e lattice antiferromagnet potassium jarosite (K jarosite: ${\mathrm{KFe}}_{3}{(\mathrm{OH})}_{6}{(\mathrm{S}\mathrm{O}}_{4}{)}_{2})$ by means of powder neutron diffraction. Extremely high degeneracy of the ground states prevents the long-range Magnetic Ordering at any temperature and the $\sqrt{3}\ifmmode\times\else\texttimes\fi{}\sqrt{3}$ structure is predicted theoretically to be favored rather than the $q=0$ structure at $T=0$ in a kagom\'e lattice Heisenberg antiferromagnet. Nevertheless, K jarosite shows long-range Magnetic Ordering at 65 K and the ordered Magnetic structure was found to be the $q=0$ structure. In addition, although the $q=0$ structure has two degenerated states of ``positive'' and ``negative'' chirality, the observed Magnetic structure contains only elemental triangles of positive chirality. We found that a weak single-ion-type anisotropy is crucial for selecting the observed Magnetic structure. The long-range Magnetic Ordering at finite temperature in the jarosite family of compounds can be ascribed to this anisotropy.
Jacques K Desmarais - One of the best experts on this subject based on the ideXlab platform.
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spin localization Magnetic Ordering and electronic properties of strongly correlated ln 2 o 3 sesquioxides ln la ce pr nd
Physical Review B, 2018Co-Authors: Kh E Elkelany, Corentin Ravoux, Jacques K Desmarais, Pietro Cortona, Yuanming Pan, John S Tse, Alessandro ErbaAbstract:Lanthanide sesquioxides are strongly correlated materials characterized by highly localized unpaired electrons in the f band. Theoretical descriptions based on standard density functional theory (DFT) formulations are known to be unable to correctly describe their peculiar electronic and Magnetic features. In this study, electronic and Magnetic properties of the first four lanthanide sesquioxides in the series are characterized through a reliable description of spin localization as ensured by hybrid functionals of the DFT, which include a fraction of nonlocal Fock exchange. Because of the high localization of the f electrons, multiple metastable electronic configurations are possible for their ground state depending on the specific partial occupation of the f orbitals: the most stable configuration is here found and characterized for all systems. Magnetic Ordering is explicitly investigated, and the higher stability of an antiferroMagnetic configuration with respect to the ferroMagnetic one is predicted. The critical role of the fraction of exchange on the description of their electronic properties (notably, on spin localization and on the electronic band gap) is addressed. In particular, a recently proposed theoretical approach based on a self-consistent definition—through the material dielectric response—of the optimal fraction of exchange in hybrid functionals is applied to these strongly correlated materials.
