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Reinhardt, Peter; Habas, Marie-Pierre; Dovesi, Roberto; Moreira, Ibério de P. R.; Illas, Francesc

doi:10.1103/physrevb.59.1016

Cited by 37 publications

(39 citation statements)

References 41 publications

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“…However, it is shown that in some cases the mappings between the Ising and the Heisenberg Hamiltonians justify the extracting of magnetic coupling constants with the Ising Hamiltonian. [2][3][4][5] For a general spin dimer it is proved that the highest spin (HS) state is an eigenstate of both the Heisenberg and the Ising Hamiltonians with the same eigenvalue and that the eigenvalue of the Ising Hamiltonian for the broken symmetry (BS) spin state is the same as the expectation value of the Heisenberg Hamiltonian for the same BS spin state. 5 Since the Heisenberg Hamiltonian has not exactly been solved for dimensions above one, it is not possible to build a general mapping between the Heisenberg and the Ising Hamiltonians.…”

Section: Introductionmentioning

confidence: 99%

Magnetic coupling constants from a hybrid density functional with 35% Hartree-Fock exchange

Feng¹,

Harrison

2004

Phys. Rev. B

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are calculated with a hybrid density functional, in which 35% of the nonlocal Hartree-Fock exchange is mixed in the general gradient approximation to the density functional theory. The theoretical magnetic coupling constants for these materials with different structures, spins, and magnetic orderings are in good agreement with experiment. Our results improve significantly over the so-called B3LYP hybrid density functional, which usually overestimates the magnetic coupling constants by about 50%. However, the energy gaps from the B3LYP functional are in better agreement with experiment than the hybrid functional with 35% Hartree-Fock exchange, which means that within the current scheme of hybrid density functionals different functionals are needed to better predict different properties of materials.

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Section: Introductionmentioning

confidence: 99%

Magnetic coupling constants from a hybrid density functional with 35% Hartree-Fock exchange

Feng¹,

Harrison

2004

Phys. Rev. B

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“…The cluster model contains a quantum-mechanical part and a proper representation of the rest of the crystal by means of a simple and convenient embedding procedure. As in previous researches, 14,52,53,62,[73][74][75][76][77][78][79][80] the quantummechanical part contains the two magnetic centers of interest and the anions in the proper coordination sphere. The final cluster models thus designed are Ni 2 O 11 and Ni 2 O 10 depending on whether the Ni-O-Ni magnetic path corresponds to an angle of 180°͑single bridge͒ or 90°͑double bridge͒.…”

Section: B Cluster Model Approachmentioning

confidence: 99%

Effect of Fock exchange on the electronic structure and magnetic coupling in NiO

2002

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The effect of Fock exchange on the periodic description of the geometrical structure, elastic constants, and electronic and magnetic properties of NiO is analyzed. Hybrid density functionals which combine a portion of ''exact'' Fock exchange with conventional local density approximation ͑LDA͒ or generalized gradient approximation ͑GGA͒ functionals remedy a number of serious inconsistencies with the traditional LDA or GGA descriptions of this prototypical ''Mott'' insulator. For example, the hybrid B3LYP functional ͑which mixes ϳ20% Fock exchange with GGA functionals͒ introduces a significant insulating gap and yields antiferromagnetic Heisenberg coupling constants between Ni sites (J 2 ) in semiquantitative agreement with experiment. Closer inspection shows that while the B3LYP orbital band gap is in excellent agreement with experiment, the magnitude of the antiferromagnetic coupling is overestimated by slightly more than 50%. This has led us to examine a simplified model which combines Fock exchange with the LDA exchange and correlation functionals. This combination allows us to study the magnitude and nature of the band gap, the magnitude of the unpaired spin densities in the different magnetic phases, and the two most important magnetic coupling constants as a function of the fraction of Fock exchange included. It is concluded that ϳ35% Fock exchange gives a reasonably balanced description of all properties, including structural parameters, magnetic form factors, the antiferromagnetic Ni-Ni exchange constant, and the character and magnitude of the band gap.

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“…25,60 Usually, the different broken symmetry solutions are found by doubling the unit cell in the appropriate direction. 25,26,37,61 However, in the case of LaMnO 3 there are several possible broken symmetry solutions within the primitive unit cell. Following the work of Su et al 29 we have chosen to study the four lowest broken symmetry solutions; this will permit a detailed comparison with the previous UHF calculations and allows us to isolate the important effects of the different hybrid functionals on their relative energies.…”

Section: Magnetic Ordering and Phasesmentioning

confidence: 99%

“…Notice that with this definition positive ͑negative͒ values of the magnetic coupling constant mean ferromagnetic ͑antiferromagnetic͒ interactions. Using the mapping procedure described in previous works 26,60,61 an overdetermined set of three equations and two unknowns is obtained. These are…”

Section: Magnetic Ordering and Phasesmentioning

confidence: 99%

Electronic and magnetic structure ofLaMnO3from hybrid periodic density-functional theory

2004

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The electronic and magnetic structures of the LaMnO 3 compound have been studied by means of periodic calculations within the framework of spin polarized hybrid density-functional theory. In order to quantify the role of approximations to electronic exchange and correlation three different hybrid functionals have been used which mix nonlocal Fock and local Dirac-Slater exchange. Periodic Hartree-Fock results are also reported for comparative purposes. The A-antiferromagnetic ground state is properly predicted by all methods including Hartree-Fock exchange. In general, the different hybrid methods provide a rather accurate description of the band gap and of the two magnetic coupling constants, strongly suggesting that the corresponding description of the electronic structure is also accurate. An important conclusion emerging from this study is that the nature of the occupied states near the Fermi level is intermediate between the Hartree-Fock and local density approximation descriptions with a comparable participation of both Mn and O states.

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Magnetic coupling in the weak ferromagnetCuF2

Cited by 37 publications

References 41 publications

Magnetic coupling constants from a hybrid density functional with 35% Hartree-Fock exchange

Magnetic coupling constants from a hybrid density functional with 35% Hartree-Fock exchange

Effect of Fock exchange on the electronic structure and magnetic coupling in NiO

Electronic and magnetic structure ofLaMnO3from hybrid periodic density-functional theory

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