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We achieve strong magnon-magnon coupling experimentally between edge and center modes in patterned hexagonal CoFeB films. The coupling strength is adjustable via the external magnetic field's direction and the nanomagnet's aspect ratio. Micromagnetic simulation indicates that the stable existence of the center mode determines the occurrence of coupling, which correlates with the direction of the edge demagnetization field. This work offers a novel perspective on the study of magnon-magnon coupling in a single material, which benefits magnon-based quantum information technology. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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.

As new information carriers, antiferromagnetic magnons have great potential in the fields of spintronics and quantum information. However, the strong exchange interaction between sublattice spins in conventional antiferromagnets results in their frequencies up to the terahertz (THz) range, hindering further exploration of related applications and physics. Recently, emerging van der Waals A‐type antiferromagnets with the weak exchange interaction may bring about a change. In this study, it demonstrates two distinct tunable ultrastrong magnon–magnon couplings in the gigahertz (GHz) band using this type of antiferromagnet, CrPS4, with a maximum normalized coupling strength (η) of 0.31. It establishes orthorhombic and monoclinic models for theoretical analyses, unambiguously showing that the ultrastrong coupling strength is caused by unique magnetocrystalline anisotropy rather than exchange enhancement. Furthermore, for the first time, it observes a continuous switching process of sublattice magnon chirality arising from the orthorhombic nature of anisotropy. These findings not only deepen the understanding of antiferromagnetic spin dynamics but also offer a powerful platform for building magnonic quantum systems and chirality‐based spintronics. [ABSTRACT FROM AUTHOR]

As new information carriers, antiferromagnetic magnons have great potential in the fields of spintronics and quantum information. However, the strong exchange interaction between sublattice spins in conventional antiferromagnets results in their frequencies up to the terahertz (THz) range, hindering further exploration of related applications and physics. Recently, emerging van der Waals A‐type antiferromagnets with the weak exchange interaction may bring about a change. In this study, it demonstrates two distinct tunable ultrastrong magnon–magnon couplings in the gigahertz (GHz) band using this type of antiferromagnet, CrPS4, with a maximum normalized coupling strength (η) of 0.31. It establishes orthorhombic and monoclinic models for theoretical analyses, unambiguously showing that the ultrastrong coupling strength is caused by unique magnetocrystalline anisotropy rather than exchange enhancement. Furthermore, for the first time, it observes a continuous switching process of sublattice magnon chirality arising from the orthorhombic nature of anisotropy. These findings not only deepen the understanding of antiferromagnetic spin dynamics but also offer a powerful platform for building magnonic quantum systems and chirality‐based spintronics. [ABSTRACT FROM AUTHOR]

Hybrid dynamical systems have gained a huge momentum not only due to their exotic physical properties but also their compelling engineering standpoint, particularly owing to their potential for coherent information processing. Remarkably, magnon–magnon coupling is experimentally identified in Ni80Fe20 nanocross array with the number of spins reaching a very low value of ≈1012. Moreover, the coupling strength is effectively tuned via different external parameters, viz. microwave excitation power and the bias‐field orientation. Extensive simulations reveal that both the static and dynamical dipolar coupling contribute to the observed anticrossing phenomenon. Simultaneously, mode‐softening of spin wave tunable by subtle changes of bias‐field orientation is also observed. The findings can greatly enrich various hybrid phenomena with a magnonic platform. [ABSTRACT FROM AUTHOR]

Traditional electronics rely on charge currents for controlling and transmitting information, resulting in energy dissipation due to electron scattering. Over the last decade, magnons, quanta of spin waves, have emerged as a promising alternative. This perspective article provides a brief review of experimental and theoretical studies on quantum and hybrid magnonics resulting from the interaction of magnons with other quasiparticles in the GHz frequency range, offering insights into the development of functional magnonic devices. In this process, we discuss recent advancements in the quantum theory of magnons and their coupling with various types of qubits in nanoscale ferromagnets, antiferromagnets, synthetic antiferromagnets, and magnetic bulk systems. Additionally, we explore potential technological platforms that enable new functionalities in magnonics, concluding with future directions and emerging phenomena in this burgeoning field., (© 2024 IOP Publishing Ltd.)

• The anti-crossing gap g c enhances 80 Hz by changing the radio frequency (rf) microwave power, which could be ascribed to the enhancement of the dipolar interaction and spin pumping effect. • Furthermore, the g c decreases with the increasing angle θ between external magnetic field and rf current due to the increase of the damping. Magnon-quasiparticle couplings perform magnon information transferences and transports, thus controlling the coupling strengths is significant for novel information function devices. Here, we report the modulation of the magnon-magnon (M−M) coupling strength in Y 3 Fe 5 O 12 /permalloy (YIG/Py) heterostructures via ferromagnetic resonance (FMR) technique. The anti-crossing gap g c enhances 80 Hz by changing the radio frequency (rf) microwave power, which could be ascribed to the enhancement of the dipolar interaction and spin pumping effect. Furthermore, the g c decreases with the increasing angle θ between external magnetic field and rf current due to the increase of magnon relaxation. Moreover, the FMR linewidths change with increasing angle θ due to the magnetic anisotropy parameters and the two-magnon relaxation mechanism induced by the more oblique external field. [ABSTRACT FROM AUTHOR]

• In a synthetic antiferromagnet (SAF), • at the present of an in-plane magnetic anisotropy, the magnon-magnon coupling arises and its strength is anisotropic; • with in-plane uniaxial magnetic anisotropy, the maximum of magnon-magnon coupling occurs when magnetic field along 45° deviates from the easy axis; • with in-plane magnetic anisotropy, the dynamical phase between two magnetic layers is neither 0° nor 180° and changes with the magnetic field. • the magnon-magnon coupling can be maximally regulated by the in-plane magnetic anisotropy field. The magnon–magnon coupling is the key issue to exchange information in hybrid magnonic systems. We investigate the magnon–magnon coupling in a synthetic antiferromagnet (SAF) system with the presence of an in-plane uniaxial magnetic anisotropy via micromagnetic simulations. The magnon–magnon coupling arises, and its strength is field-direction dependent. The maximum magnon–magnon coupling occurs when the in-plane magnetic field along 45° deviates from the easy axis. The magnon–magnon coupling can be regulated by the in-plane magnetic anisotropy field. The dynamical phase between two magnetic layers is neither 0° nor 180°, which indicates the magnon in a hybrid mode. This study provides a simple method for a tunable magnon–magnon coupling in SAFs to realize a practical hybrid quantum system based on magnonics. [ABSTRACT FROM AUTHOR]

We report here an experimental observation of dynamic dipolar coupling induced magnon-magnon coupling and spin wave (SW) mode splitting in Ni 80 Fe 20 cross-shaped nanoring array. Remarkably, we observe an anticrossing feature with minimum frequency gap of 0.96 GHz and the corresponding high cooperativity value of 2.25. Interestingly, splitting of the highest frequency SW mode occurs due to the anisotropic dipolar interactions between the cross nanorings. Furthermore, using micromagnetic simulations we demonstrate that the coupled SW modes propagate longer as opposed to other modes present in this system. Our work paves the way towards integrated hybrid systems-based quantum magnonics and on-chip coherent information transfer., (© 2021 IOP Publishing Ltd.)