Magneto-optical effects in transition metal systems

Ebert, H.

doi:10.1088/0034-4885/59/12/003

Cited by 459 publications

(363 citation statements)

References 357 publications

(544 reference statements)

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“…7 with previous results from circular magnetic x-ray dicroism ͑CMXD͒ measurements and fully relativistic spinpolarized Korringa-Kohn-Rostocker ͑SP-KKR͒ calculations. 34,35 The systematic trend that was found in the previous studies is approximately reproduced by our calculations.…”

Section: B Orbital Momentsupporting

confidence: 89%

Spin-orbit induced noncubic charge distribution in cubic ferromagnets. II. Tight-binding analysis

2002

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The orbital moment and the noncubic charge distribution in ferromagnetic transition metals with cubic lattice symmetry are investigated within the tight-binding model. By combining the tight-binding approximation, perturbation theory, and the Green's function formalism for impurity scattering, approximate expressions for both effects are derived that depend only on the spin-orbit coupling strength and the density of states of the system without spin-orbit coupling. The basic relations between the orbital moment, the noncubic charge distribution, and the band structure are derived from the form of these expressions and from their application to various model band structures: We explain in this way the scaling with the spin-orbit coupling strength and bandwidth, the typical order of magnitude, the variation as a function of the band filling, the sensitivity to band structure details, and the role of the splitting between spin-up and spin-down states. For the noncubic charge distribution we derive the form of the dependence on the direction of the magnetization and show how the sign and magnitude of this anisotropy are related to the different energy distributions of e g and t 2g states. This tight-binding analysis is finally applied to the 5d impurities in Fe. The local densities of states without spin-orbit coupling are obtained by self-consistent augmented plane-wave calculations using a supercell method. The special features of the 5d impurities in Fe with respect to the band structure, the orbital moment, and the noncubic charge distribution are discussed. The general trend of the systematics is interpreted as a band filling effect. The prevailing sign of the anisotropy is ascribed to the concentration of the e g states near the Fermi energy. The results of the tight-binding analysis are compared with the experiment and a more rigorous calculation.

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Section: B Orbital Momentsupporting

confidence: 89%

Spin-orbit induced noncubic charge distribution in cubic ferromagnets. II. Tight-binding analysis

2002

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“…The breaking of the valley degeneracy arises from the interaction of the antiferromagnetic order and the intrinsic SOC [10]. Next, we calculated the optical Hall conductivity σ xy (ω) using the Kubo-Greenwood formula [15,16],…”

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Gate-Controllable Magneto-optic Kerr Effect in Layered Collinear Antiferromagnets

2016

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Using symmetry arguments and a tight-binding model, we show that for layered collinear antiferromagnets, magneto-optic effects can be generated and manipulated by controlling crystal symmetries through a gate voltage. This provides a promising route for electric field manipulation of the magneto-optic effects without modifying the underlying magnetic structure. We further demonstrate the gate control of magneto-optic Kerr effect (MOKE) in bilayer MnPSe3 using first-principles calculations. The field-induced inversion symmetry breaking effect leads to gate-controllable MOKE whose direction of rotation can be switched by the reversal of the gate voltage.PACS numbers: 75.50. Ee,75.70.Ak,78.20.Ls,85.70.Sq Magneto-optic effects are one of the defining features of time-reversal (T ) symmetry breaking in matter. Usually, the T symmetry is broken either by an external magnetic field, or by the spontaneous appearance of a macroscopic magnetization such as in ferromagnets. Similar to their ferromagnetic counterparts, the T symmetry is also broken in antiferromagnets. However, because of their vanishing net magnetization one would naively expect an absence of magneto-optic effects in antiferromagnets. This assumption has been recently challenged by the theoretical demonstration of a rather large magneto-optic Kerr effect (MOKE) in certain non-collinear antiferromagnets with zero net magnetization [1]. This effect is closely related to the anomalous Hall effect predicted in the same class of materials [2,3], both of which are dictated by the absence of certain crystal symmetries. The appearance of magneto-optic effects in antiferromagnets is of intrinsic interest, since it would allow direct detection of the magnetic order and therefore could be useful for antiferromagnets-based memory devices [4].While non-collinear antiferromagnets have been the focus of recent interest [1][2][3], in this Letter we show that magneto-optic effects can also exist in the more commonly available collinear antiferromagnets. We start by analyzing the general symmetry requirements for magneto-optic effects, and demonstrate the symmetry principles by constructing a tight-binding model with a collinear Néel type order. We show that, contrary to the general belief, lifting the spin degeneracy of the energy bands is not a sufficient condition to generate magnetooptic effects; it is the crystal symmetry that actually controls these effects.Based on this understanding, we predict that a perpendicular electric field can be used to generate and control the MOKE in layered antiferromagnets using firstprinciples calculations. Recent theoretical and experimental progress has identified several layered compounds as promising candidates to host magnetism in their thinfilm limit [5][6][7][8][9][10]. One of them is MnPSe 3 , a semiconductor with collinear antiferromagnetic order within each layer. We show that the field-induced inversion (I) symmetry breaking in bilayer MnPSe 3 gives rise to a MOKE whose direction of rotation can be switched by the reversal...

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“…Orbital magnetic moment plays a crucial role in determining many important effects in magnetic materials such as magnetic crystalline anisotropy, non-collinear magnetism, magneto-optical Kerr effect etc.. 7 It is a well known fact that crystal field interaction quenches the orbital magnetic moment in systems containing 3d-transition metal. Accordingly, it is assumed that because of strong crystalline field on Fe 2+ ions from the surrounding Br − , the orbital moment will also get quenched in FeBr 2 .…”

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confidence: 99%

Large orbital magnetic moment and Coulomb correlation effects inFeBr2

2002

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We have performed an all-electron fully relativistic density functional calculation to study the magnetic properties of FeBr2. We show for the first time that the correlation effect enhances the contribution from orbital degrees of freedom of d electrons to the total magnetic moment on Fe 2+ as opposed to common notion of nearly total quenching of the orbital moment on Fe 2+ site. The insulating nature of the system is correctly predicted when the Hubbard parameter U is included. Energy bands around the gap are very narrow in width and originate from the localized Fe-3d orbitals, which indicates that FeBr2 is a typical example of the Mott insulator.PACS numbers: 74.25. Ha, 71.27.+a, FeX 2 (X= Cl, Br, I) are well known model systems for the study of antiferromagnetism. 1 They show unusual metamagnetic behavior wherein they undergo a phase transition from the antiferromagnetic to a saturated paramagnetic phase as a function of external magnetic field and temperature. FeBr 2 has a layered structure, where the ferromagnetic Fe layers are widely separated by non-magnetic halogen layers producing a quite weak interlayer antiferromagnetic interactions (T N = 14.2 K). The long range antiferromagnetic ordering can be overcome by applying an external magnetic field (∼ 30 kOe) parallel to the c-axis. 2 As a result, many theoretical 3 and experimental 4,5 works on FeBr 2 have been concentrated on probing the axial magnetic phase diagram, to predict and understand anomalies near the antiferromagnetic to the paramagnetic phase boundary.In addition, the electronic structures of transition metal dihalide system are of interest because they show various types of interesting behavior due to the strong correlation effect in the transition metal ion. 6 For example, they behave as a Mott insulator or charge transfer type insulator depending upon the relative size of charge transfer energy ∆ and the intra-orbital correlation energy U of the d-electrons.Although large amount of work is done to understand the anomalies in the phase diagram and the correlation effects, surprisingly no electronic structure is known from the first principles calculation. In this report, we study the electronic and magnetic properties of one of these systems (FeBr 2 ) by combining a first principles method and the Hubbard on-site correlation term.Orbital magnetic moment plays a crucial role in determining many important effects in magnetic materials such as magnetic crystalline anisotropy, non-collinear magnetism, magneto-optical Kerr effect etc.. 7 It is a well known fact that crystal field interaction quenches the orbital magnetic moment in systems containing 3d-transition metal. Accordingly, it is assumed that because of strong crystalline field on Fe 2+ ions from the surrounding Br − , the orbital moment will also get quenched in FeBr 2 . 8 Ropka, Michalski, and Radwanski 9 showed that the orbital moment is not quenched fully by the crystal field through their quasi-atomic calculation. Ropka et al. ascribed the origin of the large orbital moment to spi...

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Magneto-optical effects in transition metal systems

Cited by 459 publications

References 357 publications

Spin-orbit induced noncubic charge distribution in cubic ferromagnets. II. Tight-binding analysis

Spin-orbit induced noncubic charge distribution in cubic ferromagnets. II. Tight-binding analysis

Gate-Controllable Magneto-optic Kerr Effect in Layered Collinear Antiferromagnets

Large orbital magnetic moment and Coulomb correlation effects inFeBr2

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