Showing papers on "Exchange interaction published in 2023"
TL;DR: In magnetically ordered systems the Heisenberg exchange interaction between neighboring spins favors collinear alignment such as that seen in ferromagnets and antiferromagnetic materials as discussed by the authors .
Abstract: In magnetically ordered systems the Heisenberg exchange interaction between neighboring spins favors collinear alignment such as that seen in ferromagnets and antiferromagnets. The inclusion of antisymmetric exchange, also known as the Dzyaloshinskii--Moriya interaction (DMI), promotes an orthogonal arrangement between spins and is the subject of this review. The DMI interaction is responsible for chiral magnetism, spin-textured skyrmions, and magnetoelectric effects in multiferroic materials. The review, organized by measurement method, is focused on experiments that determine the DMI associated with thin film interfaces occurring in a variety of samples.
6 citations
TL;DR: In this article , a kinetic model for the population dynamics of the bright and dark exciton states as well as for the spin dynamics was developed to quantitatively describe the experimental data.
Abstract: Exciton recombination and spin dynamics in (In,Al)As/AlAs quantum dots (QDs) with indirect band gap and type-I band alignment were studied. The negligible (less than 0.2 μeV) value of the anisotropic exchange interaction in these QDs prevents the mixing of the excitonic basis states and makes the formation of spin-polarized bright excitons possible under quasi-resonant, circularly polarized excitation. The recombination and spin dynamics of excitons are controlled by the hyperfine interaction between the electron and nuclear spins. A QD blockade by dark excitons was observed in the magnetic field, that eliminates the impact of nuclear spin fluctuations. A kinetic model which accounts for the population dynamics of the bright and dark exciton states as well as for the spin dynamics was developed to quantitatively describe the experimental data.
2 citations
TL;DR: In this article , the effect of charge transfer on the band structure of LaAlO3 with charge doping was investigated and it was shown that the conducting characteristic arises from Fermi energy shifts via charge doping.
Abstract: RKKY interaction is an indirect interaction between localized magnetic moments mediated by conduction electrons. RKKY exchange interaction is mostly found in multilayer involving conductors as the non-magnetic spacer. However, recent experiment shows that LaAlO3 spacer can intermediate long-range exchange interaction even though it is an insulator. Here we study the mechanism of RKKY interaction in LaAlO3. To study the effect of charge transfer, we perform a density functional theory (DFT) approach to obtain the band structure of LaAlO3 with charge doping. Undoped LaAlO3 has an indirect band gap around 3 eV with peak valence at R symmetry point and lowest conduction point at Γ point. We show that the conducting characteristic arises from Fermi energy shifts via charge doping. By adding charge doping, we show that LaAlO3 can have conductor characteristics, in agreement with the charge transfer experiment on LaAlO3. The spin-polarized conduction electron is measurable as additional magnetization of the system. Furthermore, the conducting LaAlO3 is able to mediate RKKY interaction in spin valve structure.
1 citations
TL;DR: In this article , momentum-dependent anisotropic exchange interactions in cubic lattice systems are classified based on the magnetic representation analysis and an effective spin model for centrosymmetric cubic space groups, such as Pm\bar{3}m$ and Pm \bar{4}3m$, is presented.
Abstract: Multiple-$Q$ states manifest themselves in a variety of noncollinear and noncoplanar magnetic structures depending on the magnetic interactions and lattice structures. In particular, cubic-lattice systems can host a plethora of multiple-$Q$ states, such as magnetic skyrmion and hedgehog lattices. We here classify momentum-dependent anisotropic exchange interactions in the cubic-lattice systems based on the magnetic representation analysis. We construct an effective spin model for centrosymmetric cubic space groups, $Pm\bar{3}m$ and $Pm\bar{3}$, and noncentrosymmetric ones, $P\bar{4}3m$, $P432$, and $P23$: The former include the symmetric anisotropic exchange interaction, while the latter additionally include the Dzyaloshinskii-Moriya interaction. We demonstrate that the anisotropic exchange interaction becomes the origin of the multiple-$Q$ states by applying the anisotropic spin model to the case under $Pm\bar{3}$. We show several multiple-$Q$ instabilities in the ground state by performing simulated annealing. Our results will be a reference for not only exploring unknown multiple-$Q$ states but also understanding the origin of the multiple-$Q$ states observed in both noncentrosymmetric and centrosymmetric magnets like EuPtSi and SrFeO$_3$.
1 citations
TL;DR: In this paper , the authors developed an effective procedure to single out the Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction from the other exchange mechanisms in metallic two-dimensional (2D) magnetic materials.
Abstract: We developed an effective procedure to single out the Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction from the other exchange mechanisms in metallic two-dimensional (2D) magnetic materials, and applied this procedure to study two prototypical systems, 2D $\mathrm{Cr}{\mathrm{S}}_{2}$ and ${\mathrm{Fe}}_{3}\mathrm{Ge}{\mathrm{Te}}_{2}$, using first-principles calculations. In particular, the RKKY interaction is nearly independent of the lattice size in a reasonably large range and the number of $\mathrm{Cr}{\mathrm{S}}_{2}$ layers. In contrast, the other magnetic interactions such as superexchange strongly depend on the lattice size and thickness of $\mathrm{Cr}{\mathrm{S}}_{2}$ films. In ${\mathrm{Fe}}_{3}\mathrm{Ge}{\mathrm{Te}}_{2}$, the RKKY interaction is relatively weak and does not play a leading role in the magnetic structure, whereas the strong intralayer antiferromagnetic superexchange and interlayer ferromagnetic direct exchange dominate the magnetic configuration of ${\mathrm{Fe}}_{3}\mathrm{Ge}{\mathrm{Te}}_{2}$. Our work uncovers the universal role of the 2D RKKY interaction and proposes an effective way to analyze and control the magnetic coupling of 2D magnetic materials.
1 citations
22 May 2023
TL;DR: In this article , the effects of a transverse magnetic field in a Kondo lattice model with two $f$ orbitals interacting with the conduction electrons were studied, where only electrons in the localized orbital 1 interact through exchange interaction with the neighboring ones, while electrons in orbital 2 are coupled with conduction electron through Kondo interaction, and two situations can be obtained when Kondo coupling vanishes: first, a metamagnetic transition occurs just before or at the same time of the fully polarized state, and second, when the spins are already pointing out along the magnetic field.
Abstract: In this work, we study the effects of a transverse magnetic field in a Kondo lattice model with two $f$ orbitals interacting with the conduction electrons. The $f$ electrons that are present on the same site interact through Hund's coupling, while on neighboring sites they interact through intersite exchange. We consider here that part of $f$ electrons are localized (orbital 1) while another part (orbital 2) are delocalized, as it is frequent in uranium systems. Then, only electrons in the localized orbital 1 interact through exchange interaction with the neighboring ones, while electrons in orbital 2 are coupled with conduction electrons through a Kondo interaction. We obtain a solution where ferromagnetism and Kondo effect coexist for small values of an applied transverse magnetic field for $T\rightarrow0$. Increasing the transverse field, two situations can be obtained when Kondo coupling vanishes: first, a metamagnetic transition occurs just before or at the same time of the fully polarized state, and second, a metamagnetic transition occurs when the spins are already pointing out along the magnetic field.
TL;DR: In this paper , a microscopic model based on superexchange theory for a moir\'e bilayer in chromium trihalides (Cr$X_3, $X=$Br, I) is presented.
Abstract: We construct a microscopic model based on superexchange theory for a moir\'e bilayer in chromium trihalides (Cr$X_3$, $X=$Br, I). In particular, we derive analytically the interlayer Heisenberg exchange and the interlayer Dzyaloshinskii-Moriya interaction with arbitrary distances (x) between spins. Importantly, our model takes into account sliding and twisting geometries in the interlayer $X$-$X$ hopping processes. Our approach can directly access the $x$-dependent interlayer exchange without large unit-cell calculations. We argue that deducing interlayer exchange by various sliding bilayers may lead to an incomplete result in a moir\'e bilayer. Using the \textit{ab initio} tight-binding Hamiltonian, we numerically evaluate the exchange interactions in CrI$_3$. We find that our analytical model agrees with previous comprehensive density functional theory studies. Furthermore, our findings reveal the important role of the correlation effects in the $X$'s $p$ orbitals, which gives rise to a rich interlayer magnetic interaction with remarkable tunability.
TL;DR: In this paper , the authors analyzed possible ways to calculate magnetic exchange interactions within the density functional theory plus dynamical mean field theory (DFT+DMFT) approach in the paramagnetic phase.
Abstract: We analyze possible ways to calculate magnetic exchange interactions within the density functional theory plus dynamical mean-field theory (DFT+DMFT) approach in the paramagnetic phase. Using the susceptibilities obtained within the ladder DMFT approach together with the random phase approximation result for the Heisenberg model, we obtain bilinear exchange interactions. We show that the earlier obtained result of Stepanov et al. [Phys. Rev. Lett. 121, 037204 (2018); Phys. Rev. B 105, 155151 (2022)] corresponds to considering individual magnetic moments in each orbital in the leading-order approximation in the non-local correlations. We consider a more general approach and apply it to evaluate the effective magnetic parameters of iron and nickel. We show that the analysis, based on the inverse orbital-summed susceptibilities, yields reasonable results for both, weak and strong magnets. For iron we find, in the low-temperature limit, the exchange interaction $J_0\simeq 0.20$ eV, while for nickel we obtain $J_0\simeq 1.2$ eV. The considered method also allows one to describe the spin-wave dispersion at temperatures $T\sim T_C$, which is in agreement with the experimental data.
05 Apr 2023
TL;DR: In this article , the exchange coupling of the triplet states of the negatively charged exciton with the spin of a magnetic atom (Mn) was analyzed and two techniques were used to access the spin structure of this magnetic complex: the resonant excitation of the excited states of X$$-$-Mn and the analysis of the emission of a negatively charged biexciton in a magnetic dot (XX$^-$)-Mn).
Abstract: Two electrons in a quantum dot (QD) can form triplet states. We analyze the exchange coupling of the triplet states of the negatively charged exciton in a QD (X$^-$, two electrons and one hole) with the spin of a magnetic atom (Mn). Two techniques are used to access the spin structure of this magnetic complex: the resonant excitation of the excited states of X$^-$-Mn and the analysis of the emission of a negatively charged biexciton in a magnetic dot (XX$^-$-Mn). The photo-luminescence (PL) excitation of X$^-$-Mn reveals excited states with a circularly polarized fine structure which strongly depends on the Mn spin state S$_z$ and gives rise to negative circular polarization emission. This fine structure arises from the coupling of the triplet states of an excited charged exciton with the Mn (X$^{-*}$-Mn) and its S$_z$ dependence can be described by a spin effective model. The recombination of XX$^-$-Mn leaves in the dot a charged exciton in its excited state and the PL structure is controlled by the coupling of triplet states of X$^{-*}$ with the Mn spin. An analysis of the polarization and magneto-optic properties of this emission gives access to the electron-hole exchange interaction within the triplets states. Comparing the fine structure of the singlet X$^-$-Mn and of the triplets of X$^{-*}$-Mn we can independently study the different source of anisotropy in the QD: the valence band mixing and the exchange interaction in an anisotropic potential
TL;DR: In this paper , a verdazyl-based complex with Co2+ ion, (p-Py-V-p-Br)2[Co(hfac)2], was successfully synthesized.
Abstract: A verdazyl-based complex with Co2+ ion, (p-Py-V-p-Br)2[Co(hfac)2], was successfully synthesized. The molecular arrangement indicates that spins on the radical and Co form a one-dimensional (1D) spin chain, where the intermolecular interaction between the radicals and the intramolecular interaction between the radical and Co exhibit threefold periodicity. The strong antiferromagnetic interaction between radical spins forms a nonmagnetic singlet dimer, yielding paramagnetic behavior associated with the residual spins on the Co2+ ion in the low-temperature region. We evaluated the anisotropic g values by analyzing the electron spin resonance powder patterns. Furthermore, we considered the spin–orbit coupling and distorted crystal fields of the Co2+ ion and explained the triaxial anisotropic behavior. We also evaluated the anisotropy of the expected effective exchange interaction between the fictitious spins on the Co2+ ions, indicating the existence of an Ising-like exchange interaction. These results demonstrate that the strong spin–orbit coupling of the Co2+ ion in the present verdazyl-based compound yields an effective spin-1/2 with anisotropic g values and Ising-like exchange interactions.
22 May 2023
TL;DR: In this paper , the magnetization of the ladder was used to identify three singlet quantum phases with isotropic exchange interactions, including the Dimer phase with frustrated F exchanges in rungs and legs.
Abstract: The magnetization $M(h)$ is used to identify three singlet quantum phases of the ladder with isotropic exchange interactions. The Dimer phase with frustrated F exchanges in rungs and legs has a first-order $M(h)$ transition at $0$ K from singlet to ferromagnetic at the saturation field $h_s$. The Haldane-DAF phase with strong F exchange in rungs and net AF exchange between rungs has continuous $M(h)$ and is adiabatically connected to the $S = 1$ Heisenberg AF chain. The AF phase with strong F exchange in legs and net AF exchange between legs has continuous $M(h)$ and is adiabatically connected to the spin-1/2 $J_1-J_2$ model with $J_1 > 0$ and $J_2 < 0$. All three singlet phases have finite gaps to the lowest triplet state.
TL;DR: In this article, the dispersion relation from spin orbit coupling (SOC) in the spin spiral was used to obtain the antiferromagnetic behavior of the spin spin in the ML NiCl2.
Abstract: Monolayer (ML) NiCl2 exhibits a strong biquadratic exchange interaction between the first neighboring magnetic atoms (B1), as demonstrated by the spin spiral model in J. Ni et al., Phys. Rev. Lett., 2021, 127, 247204. This interaction is crucial for stabilizing the ferromagnetic collinear order within the ML NiCl2. However, they neither point out the role of B1 nor discuss the dispersion relation from spin orbit coupling (SOC) in the spin spiral. As we have done in this work, these parameters might theoretically potentially be derived directly by fitting the calculated spin spiral dispersion relation. Here, we draw attention to the fact that B1 is equivalent to half of J3 in Heisenberg linear interactions and that the positive B1 partially counteracts the negative J3's impact on the spin spiral to make the ML NiCl2 ferromagnetic. The comparatively small J3 + 1/2B1 from the spin spiral led us to believe that J3 could be substituted by B1, yet it still exists and plays a crucial function in magnetic semiconductors or insulators. The dispersion relation, which we also obtain from SOC, displays weak antiferromagnetic behavior in the spin spiral.
29 Jan 2023
TL;DR: In this article , momentum-dependent anisotropic exchange interactions in cubic lattice systems are classified based on the magnetic representation analysis and an effective spin model for centrosymmetric cubic space groups, such as Pm\bar{3}m$ and Pm \bar{4}3m$, is presented.
Abstract: Multiple-$Q$ states manifest themselves in a variety of noncollinear and noncoplanar magnetic structures depending on the magnetic interactions and lattice structures. In particular, cubic-lattice systems can host a plethora of multiple-$Q$ states, such as magnetic skyrmion and hedgehog lattices. We here classify momentum-dependent anisotropic exchange interactions in the cubic-lattice systems based on the magnetic representation analysis. We construct an effective spin model for centrosymmetric cubic space groups, $Pm\bar{3}m$ and $Pm\bar{3}$, and noncentrosymmetric ones, $P\bar{4}3m$, $P432$, and $P23$: The former include the symmetric anisotropic exchange interaction, while the latter additionally include the Dzyaloshinskii-Moriya interaction. We demonstrate that the anisotropic exchange interaction becomes the origin of the multiple-$Q$ states by applying the anisotropic spin model to the case under $Pm\bar{3}$. We show several multiple-$Q$ instabilities in the ground state by performing simulated annealing. Our results will be a reference for not only exploring unknown multiple-$Q$ states but also understanding the origin of the multiple-$Q$ states observed in both noncentrosymmetric and centrosymmetric magnets like EuPtSi and SrFeO$_3$.
TL;DR: In this paper , the effects of a transverse magnetic field in a Kondo lattice model with two f orbitals interacting with the conduction electrons were studied, and the authors obtained a solution where ferromagnetism and Kondo effect coexist for small values of an applied transversal magnetic field for T → 0.
Abstract: Abstract In this work, we study the effects of a transverse magnetic field in a Kondo lattice model with two f orbitals interacting with the conduction electrons. The f electrons that are present on the same site interact through Hund’s coupling, while on neighboring sites they interact through intersite exchange. We consider here that part of f electrons are localized (orbital 1) while another part (orbital 2) are delocalized, as it is frequent in uranium systems. Then, only electrons in the localized orbital 1 interact through exchange interaction with the neighboring ones, while electrons in orbital 2 are coupled with conduction electrons through a Kondo interaction. We obtain a solution where ferromagnetism and Kondo effect coexist for small values of an applied transverse magnetic field for T → 0. Increasing the transverse field, two situations can be obtained when Kondo coupling vanishes: first, a metamagnetic transition occurs just before or at the same time of the fully polarized state, and second, a metamagnetic transition occurs when the spins are already pointing out along the magnetic field.
TL;DR: In this paper, a spin crossover (SCO) complex with sub-monolayer thickness in contact with a passivated FM film of Co on Au(111) was studied, where the molecules preserve thermal spin crossover and at the same time the high spin species show a sizable exchange interaction of > 0.9 T with the FM Co substrate.
Abstract: Spin crossover (SCO) complexes sensitively react on changes of the environment by a change in the spin of the central metallic ion making them ideal candidates for molecular spintronics. In particular, the composite of SCO complexes and ferromagnetic (FM) surfaces would allow spin-state switching of the molecules in combination with the magnetic exchange interaction to the magnetic substrate. Unfortunately, when depositing SCO complexes on ferromagnetic surfaces, spin-state switching is blocked by the relatively strong interaction between the adsorbed molecules and the surface. Here, the Fe(II) SCO complex [FeII (Pyrz)2 ] (Pyrz = 3,5-dimethylpyrazolylborate) with sub-monolayer thickness in contact with a passivated FM film of Co on Au(111) is studied. In this case, the molecules preserve thermal spin crossover and at the same time the high-spin species show a sizable exchange interaction of > 0.9 T with the FM Co substrate. These observations provide a feasible design strategy in fabricating SCO-FM hybrid devices.
11 May 2023
TL;DR: In this paper , the authors examined the time scales associated with the development of an entangled spin-singlet state in the system and found that in short time scales the effective exchange interaction between the quantum dots is of ferromagnetic type, favoring spin-triplet correlations.
Abstract: Dynamical buildup of spin-singlet correlations between the two quantum dots is investigated by means of the time-dependent numerical renormalization group method. By calculating the timeevolution of the spin-spin expectation value upon a quench in the hopping between the quantum dots, we examine the time scales associated with the development of an entangled spin-singlet state in the system. Interestingly, we find that in short time scales the effective exchange interaction between the quantum dots is of ferromagnetic type, favoring spin-triplet correlations, as opposite to the long time limit, when strong antiferromagnetic correlations develop and eventually an entangled spin-singlet state is formed between the dots. We also numerically determine the relevant time scales and show that the physics is generally governed by the interplay between the Kondo correlations on each dot and exchange interaction between the spins of both quantum dots.
TL;DR: In this article , the long-range magnetic proximity effect is observed in hybrid structures with diverse magnetic components and potential barriers of various thicknesses and compositions, and the effect is due to the effective p-d exchange interaction of acceptor-bound holes in the quantum well with d-electrons of the ferromagnet.
Abstract: Hybrid ferromagnet-semiconductor systems possess new outstanding properties, which emerge when bringing magnetic and semiconductor materials into contact. In such structures, the long-range magnetic proximity effect couples the spin systems of the ferromagnet and semiconductor on distances exceeding the carrier wave function overlap. The effect is due to the effective p-d exchange interaction of acceptor-bound holes in the quantum well with d-electrons of the ferromagnet. This indirect interaction is established via the phononic Stark effect mediated by the chiral phonons. Here, we demonstrate that the long-range magnetic proximity effect is universal and observed in hybrid structures with diverse magnetic components and potential barriers of various thicknesses and compositions. We study hybrid structures consisting of a semimetal (magnetite Fe3O4) or dielectric (spinel NiFe2O4) ferromagnet and a CdTe quantum well separated by a nonmagnetic (Cd,Mg)Te barrier. The proximity effect is manifested in the circular polarization of the photoluminescence corresponding to the recombination of photoexcited electrons with holes bound to shallow acceptors in the quantum well induced by magnetite or spinel itself, in contrast to interface ferromagnet in case of metal-based hybrid systems. A nontrivial dynamics of the proximity effect is observed in the studied structures due to recombination-induced dynamic polarization of electrons in the quantum well. It enables the determination of the exchange constant Δexch ≈ 70 μeV in a magnetite-based structure. The universal origin of the long-range exchange interaction along with the possibility of its electrical control offers prospects for the development of low-voltage spintronic devices compatible with existing solid-state electronics.
TL;DR: Theoretical calculations of temperature-dependent magnetization in FeGd alloys were done with the use of Heisenberg-type atomistic spin Hamiltonian and Monte Carlo algorithms as discussed by the authors .
Abstract: Theoretical calculations of the temperature-dependent magnetization in FeGd alloys were done with the use of Heisenberg-type atomistic spin Hamiltonian and Monte Carlo algorithms. The random allocation of atoms in the desired crystal structure was used for simulations of magnetically amorphous alloys. Performed calculations for the two different crystal structures have shown an important role of coordination number on the observed critical temperature and compensation point. Moreover, the value of the exchange interaction between Fe and Gd sublattices plays a key role in the simulations—an increase in the Fe–Gd exchange constant provides an increase in critical temperature for each concentration of elements, which explains the higher temperature stabilization of Gd moments. It was shown that obtained temperature-dependent magnetization behavior is consistent with experimental observations, which confirms the applicability of the atomic model used to study FeGd or other magnetic alloy structures.
TL;DR: In this article , the effects of Mn and Co doping on the electronic properties, magnetic exchange interaction, and Curie temperature of intermetallic Ni2MnGa by Green's function based Korringa-Kohn-Rostoker method with coherent potential approximation (KKR-CPA).
TL;DR: In this paper , the super-exchange magnetic interaction of Fe3+-O2--Cr3+ taking place between BiFeO3/LaCrO3 nanocomposite was investigated.
Abstract: Herein, we report a successful attempt to synthesise a material based on the theory proposed by Goodenough and Kanamori et al. This report details the super-exchange magnetic interaction of Fe3+-O2--Cr3+ taking place between BiFeO3/LaCrO3 nanocomposite. The tilt in FeO6's octahedral sites cancels out the tilt in the CrO6 site, making it an ideal perovskite explained through nearest neighbouring interaction (NN), with the next nearest neighbour interaction (NNN) pointing the way to possible ferromagnetic exchange in Fe3+-O2--Cr3+. The significant enhancement of retentivity (residual magnetism) in BiFeO3/LaCrO3 nanocomposite is three times that of the pristine material. The material's high coercive nature (351.35 Oe) makes it suitable for hard magnet applications. The correlation between magnetic anisotropy value and the first-order derivative (dM/dH) of M − H data concludes the successful construction of Fe–O–Cr interaction for magnetic applications.
TL;DR: In this article , the correlation between internal energy and magnetism at each site within the framework of the Ising model is analyzed using Monte Carlo simulation, and the exchange couplings that were obtained are JCu−Ir=2.40meV, JCu −Cu=−2.00meV and JIr−Ir =0.365meV.
28 Mar 2023
TL;DR: In this article , the role of intersublattice exchange interaction on both longitudinal and transverse dynamics is analyzed with a Landau Lifshitz Bloch description of ferromagnetically coupled Fe and Ni sublattices.
Abstract: We report about element specific measurements of ultrafast demagnetization and magnetization precession damping in Permalloy (Py) thin films. Magnetization dynamics induced by optical pump at $1.5$eV is probed simultaneously at the $M_{2,3}$ edges of Ni and Fe with High order Harmonics for moderate demagnetization rates (less than $50$%). The role of the intersublattice exchange interaction on both longitudinal and transverse dynamics is analyzed with a Landau Lifshitz Bloch description of ferromagnetically coupled Fe and Ni sublattices. It is shown that the intersublattice exchange interaction governs the dissipation during demagnetization as well as precession damping of the magnetization vector.
TL;DR: In this article , a quantum approach to electron-hole exchange was proposed, which makes use of the second quantization formalism to describe the problem in terms of Bloch-state electron operators and renders transparent the fact that such singular effect comes from interband Coulomb processes.
Abstract: We propose a quantum approach to ``electron-hole exchange,'' better named electron-hole pair exchange, that makes use of the second quantization formalism to describe the problem in terms of Bloch-state electron operators. This approach renders transparent the fact that such singular effect comes from interband Coulomb processes. We first show that, due to the sign change when turning from valence-electron destruction operator to hole creation operator, the interband Coulomb interaction only acts on spin-singlet electron-hole pairs, just like the interband electron-photon interaction, thereby making these spin-singlet pairs optically bright. We then show that, when written in terms of reciprocal lattice vectors ${\mathbf{G}}_{m}$, the singularity of the interband Coulomb scattering in the small wave-vector transfer limit entirely comes from the ${\mathbf{G}}_{m}=\mathbf{0}$ term, which renders its singular behavior easy to calculate. Comparison with the usual real-space formulation in which the singularity appears through a sum of ``long-range processes'' over all ${\mathbf{R}}_{\ensuremath{\ell}}\ensuremath{
e}\mathbf{0}$ lattice vectors once more proves that periodic systems are easier to handle in terms of reciprocal vectors ${\mathbf{G}}_{m}$ than in terms of lattice vectors ${\mathbf{R}}_{\ensuremath{\ell}}$. Well-accepted consequences of the electron-hole exchange on excitons and polaritons are reconsidered and refuted for different major reasons.
TL;DR: In this article , a model of nonequilibrium thermodynamics of erbium orthoferrite is presented, where quantum-mechanical effects in arbitrary magnetic fields, related both to the direction of a general quantization axis and an influence of anisotropic exchange interactions on the magnetic structure, spin-reorientation phase transition, spin reversals, and hysteresis, are considered.
Abstract: A model of nonequilibrium thermodynamics of erbium orthoferrite is presented. The quantum-mechanical effects in arbitrary magnetic fields, related both to the direction of a general quantization axis and an influence of anisotropic exchange interactions on the magnetic structure, spin-reorientation phase transition, spin reversals, and hysteresis, are considered. Based on recent experimental data on temperature-induced spin switching [Phys. Rev. B 105, 094424 (2022)], a possible mechanism for the exchange bias of magnetic hysteresis loops is proposed. The main parameters of the model Hamiltonian are determined, which point out a strongly competitive character of exchange interactions in erbium orthoferrite.
TL;DR: In this article , the authors used photoexcited charge transfer between the two ferromagnetic layers of a Co2FeAl/(Ga,Mn)As system at low laser fluence levels for low-power spin manipulation.
Abstract: Fast spin manipulation in magnetic heterostructures, where magnetic interactions between different materials often define the functionality of devices, is a key issue in the development of ultrafast spintronics. Although recently developed optical approaches such as ultrafast spin‐transfer and spin–orbit torques open new pathways to fast spin manipulation, these processes do not fully utilize the unique possibilities offered by interfacial magnetic coupling effects in ferromagnetic multilayer systems. Here, ultrafast optically controlled interfacial exchange interactions in the ferromagnetic Co2FeAl/(Ga,Mn)As system at low laser fluence levels are experimentally demonstrated. The excitation efficiency of Co2FeAl with the (Ga,Mn)As layer is 30–40 times higher than the case with the GaAs layer at 5 K due to the modification of exchange coupling interaction via photoexcited charge transfer between the two ferromagnetic layers. In addition, the coherent spin precessions persist to room temperature, excluding the drive of pump‐modulated magnetization in the (Ga,Mn)As layer and indicating a proximity‐effect‐related optical excitation mechanism. The results highlight the importance of interfacial exchange interactions in ferromagnetic heterostructures and how these magnetic coupling effects can be utilized for ultrafast, low‐power spin manipulation.