Enhancement of spin-wave nonreciprocity in magnonic crystals via synthetic antiferromagnetic coupling

Di, Kai; Feng, Si-Shen; Piramanayagam, S. N.; Zhang, V. L.; Lim, H. S.; Ng, S. C.; Kuok, M. H.

doi:10.1038/srep10153

Cited by 55 publications

(29 citation statements)

References 28 publications

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“…This effect has been observed in Refs. [64,65] for FM films with different magnetic (or geometrical) properties on top and bottom surfaces, where, basically, the symmetry is broken along the thickness by introducing different magnetic anisotropies at the surfaces [64] and by considering antiferromagnetic states between the magnetization in the grooves (d + δ < y < d) and the bottom FM film of thickness d [65]. Note that in the one-dimensional case ξ (G,k) = (G n + k z ) sin ϕ, and therefore, the nonreciprocal properties could be enhanced in the Damon-Eshbach geometry (ϕ = 90 • ), such as in the case of spin waves propagating in FM/heavy-metal alloys, where the Dzyaloshinskii-Moriya interaction is important [66][67][68][69][70][71].…”

Section: Resultsmentioning

confidence: 99%

Dipolar interaction induced band gaps and flat modes in surface-modulated magnonic crystals

et al. 2018

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Theoretical results for the magnetization dynamics of a magnonic crystal formed by grooves on the surface of a ferromagnetic film, called a surface-modulated magnonic crystal, are presented. For such a system, the role of the periodic dipolar field induced by the geometrical modulation is addressed by using the plane-wave method. The results reveal that, under the increasing of the depth of the grooves, zones with magnetizing and demagnetizing fields act on the system in such a way that magnonic band gaps are observed in both Damon-Eshbach and backward volume geometries. Particularly, in the backward volume configuration, high-frequency band gaps and lowfrequency flat modes are obtained. By taking into account the properties of the internal field induced by the grooves, the flattening of the modes and their shift towards low frequencies are discussed and explained. To test the validity of the model, the theoretical results of this work are confirmed by micromagnetic simulations, and good agreement between both methods is achieved. The theoretical model allows for a detailed understanding of the physics underlying these kinds of systems, thereby providing an outlook for potential applications on magnonic devices.

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Section: Resultsmentioning

confidence: 99%

Dipolar interaction induced band gaps and flat modes in surface-modulated magnonic crystals

et al. 2018

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“…Magnetic thin films with engineered lateral asymmetry, leading to an anisotropy gradient, has been recently proposed for skyrmion control [32], and for field-free magnetization reversal, owing to a new field-like spin-orbit torque [33]. The frequency non-reciprocity can be also induced by dipolar interaction, as has been predicted in arrays of coupled magnetic nanopillars [31], magnetic nanotubes [34], and FM films where the spatial symmetry is broken along the thickness [35][36][37][38]. The latter systems suggest that the dipolar interaction, which induces non-reciprocity, becomes prominent in FM layers with some kind of graduation along the thickness, which is the focus of interest in this paper.…”

Section: Introductionmentioning

confidence: 99%

Spin-wave non-reciprocity in magnetization-graded ferromagnetic films

et al. 2019

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A theoretical approach has been developed to study the spin-wave dynamics of magnetization-graded ferromagnetic films, where the magnetic properties change along the film thickness. The theory is based on a multilayer approach, where the influence of both long-range dipolar interactions and interlayer exchange coupling between sublayers is included. This allows for instance to describe films with a continuous variation of the saturation magnetization along the thickness. A systematic study is carried out in order to analyze different profiles of the saturation magnetization, which is checked through a test of convergence. It is found that the spin-wave dispersion is significantly modified when the strength of the magnetization changes in the bulk film, where a notable frequency non-reciprocity of two counter propagating spin waves is predicted. This is associated with heterosymmetric mode profiles and a modification of the conventional quantization condition associated to perpendicular standing spin-wave modes. Micromagnetic simulations have been carried out to validate the model, where a perfect agreement is reached between both methods. These results show that magnetizationgraded ferromagnetic films can be used to channel and control spin waves, thus promoting different kinds of functionalities for magnon-based devices.

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“…These can serve as playgrounds for testing key theoretical concepts, such as those of quantum phase transitions and criticality. 2 In addition, studies of quantum magnets and spin-wave dynamics promise new applications in the fields of magnonics and spintronics, 3 where the use of antiferromagnets (AFMs) may serve to improve magnetic-storage capabilities. 4 The two-dimensional Heisenberg-type cuprates deserve special attention, since their weakly-interacting layers, characterized by a square-lattice disposition of Cu(II) ions, display remarkable structural and magnetic analogies with the copper-oxide high-T c superconductors, such as, e.g., La 2−x Sr x CuO 4 .…”

Section: Introductionmentioning

confidence: 99%

“…Since the samples are air-and water sensitive, they were constantly kept in a dessicator. 15 Three samples with different sizes were available: one large sample (81 mg, 6.5×5×1 mm 3 ) was used for the zero-pressure magnetometry, whereas the smaller ones (14 and 5.5 mg) were employed for the NMR and magnetization measurements under pressure. The single Cu(pz) 2 (ClO 4 ) 2 crystals were cut such as to have two opposite faces parallel to the bc planes.…”

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confidence: 99%

Pressure and magnetic field effects on a quasi-two-dimensional spin-12Heisenberg antiferromagnet

et al. 2016

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Cu(pz) 2 (ClO 4 ) 2 (with pz denoting pyrazine, C 4 H 4 N 2 ) is among the best realizations of a two-dimensional spin-1 /2 square-lattice antiferromagnet. Below T N = 4.21 K, its weak interlayer couplings induce a 3D magnetic order, strongly influenced by external magnetic fields and/or hydrostatic pressure. Previous work, focusing on the [H, T ] phase diagram, identified a spin-flop transition, resulting in a field-tunable bicritical point. However, the influence of external pressure has not been investigated yet. Here we explore the extended [p, H, T ] phase diagram of Cu(pz) 2 (ClO 4 ) 2 under pressures up to 12 kbar and magnetic fields up to 7.1 T, via magnetometry and 35 Cl nuclear magnetic resonance (NMR) measurements. The application of magnetic fields enhances T X Y , the crossover temperature from the Heisenberg to the X Y model, thus pointing to an enhancement of the effective anisotropy. The applied pressure has an opposite effect [dT N /dp = −0.050(8) K/kbar], as it modifies marginally the interlayer couplings, but likely changes more significantly the orbital reorientation and the square-lattice deformation. This results in a remodeling of the effective Hamiltonian, whereby the field and pressure effects compensate each other. Finally, by comparing the experimental data with numerical simulations we estimate T BKT , the temperature of the Berezinskii-Kosterlitz-Thouless topological transition and argue why it is inaccessible in our case.

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Enhancement of spin-wave nonreciprocity in magnonic crystals via synthetic antiferromagnetic coupling

Cited by 55 publications

References 28 publications

Dipolar interaction induced band gaps and flat modes in surface-modulated magnonic crystals

Dipolar interaction induced band gaps and flat modes in surface-modulated magnonic crystals

Spin-wave non-reciprocity in magnetization-graded ferromagnetic films

Pressure and magnetic field effects on a quasi-two-dimensional spin-12Heisenberg antiferromagnet

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