Search Results (14)

We investigate momentum transport in ferromagnetic–plasmon heterostructures using Keldysh field theory and energy–momentum tensor formalism. A three-layer model reveals that plasmon frequency shifts generate a non-zero expectation value for the $xz$-component of the energy–momentum tensor $⟨T_{xz}⟩$ through magnon–plasmon coupling. The momentum transport exhibits linear velocity dependence, with temperature behavior transitioning from exponential suppression at low temperatures to linear growth at high temperatures, governed by the magnon energy gap. Spatial oscillations follow $sin(2n\pi z/h)$ patterns within the ferromagnetic layer. This framework provides fundamental insights into quantum momentum transport mechanisms in magnetic systems. Full article

In this paper, we analyzed the influence of the spin Nernst effect on quantum correlation in a layered ferrimagnetic model. In the study of three-dimensional ferrimagnets, the focus is on materials with a specific arrangement of spins, where the neighboring spins are parallel and the others are antiparallel. The anisotropic nature of these materials means that the interactions between spins depend on their relative orientations in different directions. We analyzed the effect of magnon bands induced by the coupling parameters on entanglement negativity. The influence of the coupling parameters of the topologic phase transition on quantum entanglement is investigated as well. Numerical simulations using the Lanczos algorithm and exact diagonalization for different lattice sizes are compared with the results of spin wave theory. Full article

The giant magnetoresistance effect in two-dimensional (2D) magnetic materials has sparked substantial interest in various fields; including sensing; data storage; electronics; and spintronics. Their unique 2D layered structures allow for the manifestation of distinctive physical properties and precise performance regulation under different conditions. In this review, we present an overview of this rapidly developing research area. Firstly, these 2D magnetic materials are catalogued according to magnetic coupling types. Then, several vital effects in 2D magnets are highlighted together with theoretical investigation, such as magnetic circular dichroism, magneto-optical Kerr effect, and anomalous Hall effect. After that, we forecast the potential applications of 2D magnetic materials for spintronic devices. Lastly, research advances in the attracting magnons, skyrmions and other spin textures in 2D magnets are discussed. Full article

Magnons, recognized as the quanta of spin waves, offer a pathway for transmitting information without the need for electron motion, thus emerging as a leading candidate for the next generation of low-power electronics. Firstly, this study gives an overview by examining magnon modes possessing infinite wavelengths or zero wave numbers (known as ferromagnetic resonance) in classical ferromagnetic, antiferromagnetic, and synthetic antiferromagnetic systems. It delves into the dynamics of magnetization, particularly focusing on magnetic moments precession and the corresponding dispersion relationships under two distinct acoustic and optic eigenmodes. Furthermore, it elaborates on a novel hybrid quantum system termed magnon-magnon coupling. The study elucidates the mechanism behind the robust coupling between acoustic and optic magnon modes. Finally, we briefly discuss the current challenges and future research directions in this field. Full article

In this paper, we propose a scheme for measurement-based control of hybrid Einstein–Podolsky–Rosen (EPR) entanglement and steering between distant macroscopic mechanical oscillator and yttrium iron garnet (YIG) sphere in a system of an electromechanical cavity unidirectionally coupled to an electromagnonical cavity. We reveal that when the output of the electromagnonical cavity is continuously monitored by homodyne detection, not only the phonon–magnon entanglement and steering but also the purities of the phononic, magnonic and phonon–magnon states are considerably enhanced. We also find that the measurement can effectively retrieve the magnon-to-phonon steering, which is not yet obtained in the absence of the measurement. We show that unconditional phonon–magnon entanglement and steering can be achieved by introducing indirect feedback to drive the magnon and mechanical subsystems. The long-distance macroscopic hybrid entanglement and steering can be useful for, e.g., fundamental tests for quantum mechanics and quantum networks. Full article

We propose an experimental method for the unidirectional excitation of spin waves. By structuring Au nanowire arrays within a coplanar waveguide onto a thin yttrium iron garnet (YIG) film, we observe a chiral coupling between the excitation field geometry of the nanowire grating and several well-resolved propagating magnon modes. We report a propagating spin wave spectroscopy study with unprecedented spectral definition, wavelengths down to 130 nm and attenuation lengths well above 100 μm over the 20 GHz frequency band. The proposed experiment paves the way for future non-reciprocal magnonic devices. Full article

In this paper, we theoretically and experimentally study the distant magnon-magnon coupling mediated by nonresonant photons. We establish a magnon-photon-magnon coupling model for two CrCl₃ crystals spacial separated on a microstrip line. By changing the phase difference of the samples from 0 to π in order to manipulate the distant magnons from coherent coupling to dissipative coupling, our coupling model predicts that the dispersion is tunable from a level repulsion to a level attraction. In addition, we experimentally demonstrate that two spacial separated CrCl₃ crystals over a distance of 1.2 cm couple each other indirectly via the microwave photons on the microstrip line. Our works for the distant magnon-magnon coupling mediated by nonresonant photons might provide new sight into long-distant information transmission. Full article

The past few decades have witnessed the ultra-fast development of wireless telecommunication systems, such as mobile communication, global positioning, and data transmission systems. In these applications, radio frequency (RF) acoustic devices, such as bulk acoustic waves (BAW) and surface acoustic waves (SAW) devices, play an important role. As the integration technology of BAW and SAW devices is becoming more mature day by day, their application in the physical and biochemical sensing and actuating fields has also gradually expanded. This has led to a profusion of associated literature, and this article particularly aims to help young professionals and students obtain a comprehensive overview of such acoustic technologies. In this perspective, we report and discuss the key basic principles of SAW and BAW devices and their typical geometries and electrical characterization methodology. Regarding BAW devices, we give particular attention to film bulk acoustic resonators (FBARs), due to their advantages in terms of high frequency operation and integrability. Examples illustrating their application as RF filters, physical sensors and actuators, and biochemical sensors are presented. We then discuss recent promising studies that pave the way for the exploitation of these elastic wave devices for new applications that fit into current challenges, especially in quantum acoustics (single-electron probe/control and coherent coupling between magnons and phonons) or in other fields. Full article

The influence of magnon bands on entanglement in the antiferromagnetic XXZ model on a triangular lattice, which models the bilayer structure consisting of an antiferromagnetic insulator and normal metal, is investigated. This effect was studied in ferromagnetic as well as antiferromagnetic triangular lattices. Quantum entanglement measures given by the entanglement negativity have been studied, where a magnon current is induced in the antiferromagnet due to interfacial exchange coupling between localized spins in the antiferromagnet and itinerant electrons in a normal metal. Moreover, quantum correlations in other frustrated models, namely the metal-insulation antiferromagnetic bilayer model and the Heisenberg model with biquadratic and bicubic interactions, are analyzed. Full article

Hybrid quantum systems have attracted much attention due to the fact that they combine the advantages of different physical subsystems. Cavity QED (cavity quantum electrodynamics) with magnons is a hybrid quantum systems that combines a YIG (Yttrium Iron Garnet) sphere and a 3D (three-dimensional) rectangular microwave cavity. Based on this hybrid photon-magnon system, we obtain an approximate analytic solution by the RWA (rotating wave approximation) with an ingenious transformation. After skillfully diagonalizing the Hamiltonian, we show that the Kerr-nonlinearity interactions could yield a negativity value of the Wigner function, periodic quadrature squeezing effects, antibunching property, and field nonclassicality in the magnon. Our work may stimulate the study of nonclassicality of photon-magnon coupling systems and its potential applications in quantum information processing. Full article

Magnons (the quanta of spin waves) could be used to encode information in beyond Moore computing applications. In this study, the magnon coupling between acoustic mode and optic mode in synthetic antiferromagnets (SAFs) is investigated by micromagnetic simulations. For a symmetrical SAF system, the time-evolution magnetizations of the two ferromagnetic layers oscillate in-phase at the acoustic mode and out-of-phase at the optic mode, showing an obvious crossing point in their antiferromagnetic resonance spectra. However, the symmetry breaking in an asymmetrical SAF system by the thickness difference, can induce an anti-crossing gap between the two frequency branches of resonance modes and thereby a strong magnon-magnon coupling appears between the resonance modes. The magnon coupling induced a hybridized resonance mode and its phase difference varies with the coupling strength. The maximum coupling occurs at the bias magnetic field at which the two ferromagnetic layers oscillate with a 90° phase difference. Besides, we show how the resonance modes in SAFs change from the in-phase state to the out-of-phase state by slightly tuning the magnon-magnon coupling strength. Our work provides a clear physical picture for the understanding of magnon-magnon coupling in a SAF system and may provide an opportunity to handle the magnon interaction in synthetic antiferromagnetic spintronics. Full article

We study how to enhance the transverse magneto-optical Kerr effect (TMOKE) of ultra-thin magnetic dielectric films through the excitation of strong magnetic resonances on metasurface with a metal nanowire array stacked above a metal substrate with an ultra-thin magnetic dielectric film spacer. The plasmonic hybridizations between the Au nanowires and substrate result in magnetic resonances. The periodic arrangement of the Au nanowires can excite propagating surface plasmon polaritons (SPPs) on the metal surface. When the SPPs and the magnetic resonances hybridize, they can strongly couple to form two strong magnetic resonances, which are explained by a coupled oscillator model. Importantly, benefitting from the strong magnetic resonances, we can achieve a large TMOKE signal up to 26% in the ultra-thin magnetic dielectric film with a thickness of only 30 nm, which may find potential applications in nanophotonics, magnonics, and spintronics. Full article

The spin-Seebeck effect (SSE) is an advective transport process traditionally studied in bilayers composed of a ferromagnet (FM) and a non-magnetic metal (NM) with strong spin-orbit coupling. In a temperature gradient, the flux of magnons in the FM transfers spin-angular momentum to electrons in the NM, which by the inverse spin-Hall effect generates an SSE voltage. In contrast, the Nernst effect is a bulk transport phenomenon in homogeneous NMs or FMs. These effects share the same geometry, and we show here that they can be added to each other in a new combination of FM/NM composites where synthesis via in-field annealing results in the FM material (MnBi) forming aligned needles inside an NM matrix with strong spin-orbit coupling (SOC) (Bi). Through examination of the materials’ microstructural, magnetic, and transport properties, we searched for signs of enhanced transverse thermopower facilitated by an SSE contribution from MnBi adding to the Nernst effect in Bi. Our results indicate that these two signals are additive in samples with lower MnBi concentrations, suggesting a new way forward in the study of SSE composite materials. Full article

Synthetic antiferromagnets (SAF) are widely used for a plethora of applications among which data storage, computing, and in the emerging field of magnonics. In this framework, controlling the magnetic properties of SAFs via localized thermal treatments represents a promising route for building novel magnonic materials. In this paper, we study via vibration sample magnetometry the temperature dependence of the magnetic properties of sputtered exchange bias SAFs grown via magnetron sputtering varying the ferromagnetic layers and spacer thickness. Interestingly, we observe a strong, reversible modulation of the exchange field, saturation field, and coupling strength upon heating up to 250 °C. These results suggest that exchange bias SAFs represent promising systems for developing novel artificial magnetic nanomaterials via localized thermal treatment. Full article