A PROBABLE MECHANISM OF SPIN-STATE TRANSITION IN LaCoO3

Total energies and electronic structures of rhombohedral lanthanum cobaltite ( LaCoO 3) with both non-magnetic and magnetic states are calculated from generalized gradient approximation (GGA) with on-site Coulomb correlation corrections (GGA + U) method. It is found that only the non-magnetic ground state can be obtained for LaCoO 3 at 5 K, consistent with previous studies. When U = 4.0 eV is employed, the band gap is found to be 0.6 eV, in agreement with the result of ultraviolet photoemission spectroscopy (UPS). The ferromagnetic ground state can be obtained for LaCoO 3 at 100 K, but much larger on-site Coulomb interaction between Co 3d is found. Only when U = 7.8 eV is employed for the calculation of LaCoO 3 at 100 K can we find a band gap of 0.26 eV, consistent with the optical conductivity measurements. According to these results, we propose a probable mechanism for spin-state transition in LaCoO 3 at around 100 K. The transition is mainly due to the big change in the on-site Coulomb repulsion between Co 3d electrons.

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First-principles calculations of structural, electronic, magnetic, elastic and optical properties of tetragonal zircon-type CeVO4

International Journal of Modern Physics B ◽

10.1142/s0217979218502399 ◽

2018 ◽

Vol 32 (22) ◽

pp. 1850239

Author(s):

Wen-Qi Chen ◽

Hao Wang ◽

Yi Mu ◽

Cui-E Hu ◽

Yan Cheng

Keyword(s):

Optical Properties ◽

Magnetic Moment ◽

Ground State ◽

Local Density ◽

Coulomb Repulsion ◽

Lattice Parameters ◽

Experimental Result ◽

Generalized Gradient ◽

Magnetic Ground State ◽

Zircon Type

We have performed comprehensive first-principle calculations to investigate the structural, electronic, magnetic, elastic and optical properties of the tetragonal zircon-type CeVO4. The local density approximation plus U (LDA+U) and generalized gradient approximation plus U (GGA+U) methods are used to interpret the strong Coulomb repulsion among the localized Ce 4f electrons. Without the effective U parameters, the obtained ground state of the ferromagnetic (FM) metal is not consistent with the experimental result. However, we can get the antiferromagnetic (AFM2: the magnetic ground state) insulating ground state for CeVO4 by LDA+U and GGA+U. It reveals that the result is in agreement with the experiment. For AFM2 CeVO4, the dependence of properties on the U parameters has been studied in detail. The effect of spin–orbit coupling (SOC) has also been investigated in detail. The demonstrated properties include volume, lattice parameters, bandgap, the density of states (DOS) and spin magnetic moment of Ce atom. With the Hubbard U parameter around 6 eV, the lattice parameters (a=7.396 Å, V=351.82 Å3, c/a=0.874), bulk modulus B0 (121 GPa), insulating gap (2.157 eV) and magnetic moment (0.97 [Formula: see text] per Ce atom) are consistent with the experiments and other theoretical results. Besides, the elasticity-related properties and optical properties have also been calculated for U=0,2,4 and 6 eV.

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Realizing bias-induced spin transition with high-spin MnII complexes at room temperature

Journal of Materials Chemistry C ◽

10.1039/c7tc03966b ◽

2017 ◽

Vol 5 (44) ◽

pp. 11598-11604

Author(s):

Hua Hao ◽

Ting Jia ◽

Xiaohong Zheng ◽

Lingling Song ◽

Zhi Zeng

Keyword(s):

High Spin ◽

Spin State ◽

Ground State ◽

Room Temperature ◽

State Transition ◽

Spin Transition ◽

Memory Devices ◽

Spin State Transition ◽

Molecular Transistors ◽

Magnetic Ions

Complexes in the ground state with high-spin magnetic ions (3d5/3d4) can be used to realize the electrically-induced spin-state transition and build room-temperature molecular transistors or memory devices.

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