In 1930, Bloch1 proposed that when the magnetic moment in a magnetic system is disturbed, it deviates from equilibrium states. Such disturbances will propagate through the material in the form of waves, known as spin waves. Later in 1957, Brockhouse2 confirmed the existence of spin waves through neutron diffraction experiments, and the quantized units of spin waves are called magnons. Magnons, as the elementary excitations in magnetic systems, have several advantages: they propagate without generating Joule heat, exhibit wave characteristics, have intrinsic frequencies ranging from gigahertz to terahertz, and support a rich set of techniques for exciting, manipulating, and detecting their transport. Therefore, they are poised as a potential candidate to replace electrons as the carriers for the next-generation information technology. In recent years, due to advancements in research techniques for magnons, the study of magnons has attracted increasing attention. Thanks to the organization by the Editorial Board of Applied Physics Letters, we are honored to organize a special issue on the topic of Magnonics. Focusing on materials, physics, and devices related to magnonics,3 we accepted and published a total of 55 papers.

This special topic issue was proposed in Applied Physics Letters to draw more interest to this emerging field. It includes cutting-edge research in magnonics across various directions:

  1. Magnon and spin wave in ferromagnets, ferrimagnets, antiferromagnets, magnetic semiconductors, and organic materials.4–7 

  2. Excitation/generation, modulation, and detection of magnon current.8–28 

  3. Magnonic crystals and their magnon (spin wave) transport properties.29–31 

  4. Interactions among magnon, phonon, photon, and other quasiparticles.32–45 

  5. Magnon quantum effects in magnon heterostructures.46–49 

  6. Magnon devices, including magnon valve, junction, transistor, logic, and circuits.50–57 

  7. Magnonics in two-dimensional (2D) materials.58 

In the research of magnon in different magnetic materials, for example, the properties of magnons in a newly discovered magnetic material, the altermagnets, have been studied.5 Sødequist and Olsen have proposed a high-throughput computational search method for altermagnetism in two-dimensional materials based on a calculated database of 2D materials. They have calculated and predicted the magnon properties in altermagnetic materials such as RuF4 and FeBr3. In addition, the magnons at the compensation point of ferrimagnetic materials4 and in rare earth ferrimagnets7 have also been studied theoretically and experimentally.

The most studied aspects are the excitation, manipulation, and detection techniques of magnons. For instance, in antiferromagnets, due to the absence of dipole interactions, magnetic moments can quickly recover to equilibrium after perturbation, resulting in higher intrinsic frequencies of magnons. Ge et al.13 theoretically demonstrated the excitation of terahertz magnons by moving antiferromagnetic domains under the energy gradient of magnetic anisotropy, combining Lorentz contraction from relativity. The broadening of domain width leads to a reduction in anisotropic energy, which is converted into the energy for exciting magnons. Additionally, terahertz magnons in two-dimensional antiferromagnetic materials exhibit rich phenomena of magnon–plasmon coupling and magnon–photon coupling.18 In terms of manipulating magnons, for example, microwave nonreciprocal transport is achieved using pump-induced magnon modes,8 and nonreciprocal magnon couplers can be realized with metal-coated yttrium iron garnet (YIG) strips.15 Introducing local vertical magnetic anisotropy nanofilm stacks in spin wave transmission channels20 allows for fine-tuning the propagation characteristics of spin waves, such as frequency-selective coherent spin wave transmission. Zhou et al. proposed spin torque nano-oscillators,23 which enable the control of spin wave packet excitation using electric fields. They used electrically tuned magnetic droplets to generate spin waves, adjusting the amplitude and period of the spin wave packet by varying the pulse width of the electric field.

Magnon crystals possess periodic magnetic structures, where the magnon spectrum significantly differs from that of bulk materials, exhibiting bandpass phenomena for specific frequencies of magnons. In this special topic, for example, Martyshkin et al. experimentally confirmed29 that yttrium iron garnet (YIG) thin films with periodic metallic stripe arrays on the surface exhibit bandpass characteristics in the propagation of magnetostatic surface waves.

Magnons and their coupling with other particles and quasiparticles also exhibit a wealth of physical phenomena. For instance, magnon–phonon coupling provides a method to manipulate the magnon system using external stress. Xiong38 achieved controllable flipping of magnon excitations based on magnetostrictive effect. Chen et al.39 measured the thermal conductivity of 2D MnPSe3 and found that due to magnon–phonon coupling, the measured peak thermal conductivity changes with increasing thickness, and the magnon–phonon scattering rate increases with thickness, leading to a significant suppression of thermal conductivity. Bogdanova et al.40 studied the effect of stress on antiferromagnetic resonance in α-Fe2O3, employing Brillouin light scattering spectroscopy to detect the excitation of quasi-ferromagnetic and antiferromagnetic resonance modes in bulk α-Fe2O3. The results indicate that α-Fe2O3 is a suitable material for strain-controlled magnon devices.

Magnons are bosons and, like photons, can exhibit the Bose–Einstein effect. Recent experiments have confirmed this conclusion. Schweizer et al. proposed that variations in magnetization and demagnetizing fields jointly affect the local increasement in the minimum frequency value of magnon dispersion in the Bose–Einstein condensate state, which leads to a magnon superfluid away from the hot region.48 

The understanding of magnon properties in different magnetic materials and the advancement of experimental techniques have promoted the development of magnonic devices, providing many interesting potential applications in magnonics. For example, similar to the capacitors commonly used in electronics, Gunnink et al.50 proposed a magnon spin capacitor that can accumulate spin at the junction between two exchange-coupled ferromagnets. Additionally, Klima et al.54 proposed a zero-field spin wave turn, which was demonstrated through micromagnetic simulations and Brillouin light scattering microscopy experiments. They showed that dipole spin waves can propagate through a 90° turn without distortion, demonstrating the possibility of spin wave transport in curved geometric materials. Ustinov et al.56 utilized current-controlled magnonic reservoir to achieve physical reservoir computing.

Due to the influence of surface and interfacial effects, two-dimensional materials exhibit many novel properties that are distinct from their bulk counterparts. For example, Chen et al.58 studied magnons in the two-dimensional Weyl magnet Fe/W(110). They discovered that the chiral asymmetric magnon dispersion is related to the presence of Weyl fermions near the Fermi level and surface Fermi arcs. This provides an excellent example of introducing topology into the field of magnonics.

The development of electronics has laid the foundation for modern information technology and industry, greatly promoting the advancement of human technology and lifestyle. Electronics primarily relies on the charge degree of electrons, and further the spin degree of electrons is developed for information storage, transmission, and processing, i.e., spintronics. Analogously to electronics and spintronics, magnonics utilizes the quasiparticle magnon as the information carrier to avoid Joule heating. Additionally, magnons have an intrinsic frequency range from gigahertz to terahertz and possess a rich set of excitation, manipulation, and detection techniques, making them promising candidates for the next generation of information carriers and attracting significant research interest. This special topic issue on magnonics aims to introduce the cutting-edge progress in materials, physics, and devices related to magnonics, drawing more scholars into this emerging field.

We thank all authors who have contributed to this special topic issue on magnonics.

1.
V. F.
Bloch
, “
On the theory of ferromagnetism
,”
Z. Phys.
61
,
206
(
1930
).
2.
B. N.
Brockhouse
, “
Scattering of neutrons by spin waves in magnetite
,”
Phys. Rev.
106
,
859
(
1957
).
3.
X. F.
Han
,
H.
Wu
, and
T. Y.
Zhang
, “
Magnonics: Materials, physics, and devices
,”
Appl. Phys. Lett.
125
,
020501
(
2024
).
4.
L.
Sánchez-Tejerina
,
D.
Osuna Ruiz
,
E.
Martínez
,
L.
López Díaz
,
V.
Raposo
, and
Ó.
Alejos
, “
Spin waves in ferrimagnets near the angular magnetization compensation temperature: A micromagnetic study
,”
Appl. Phys. Lett.
125
,
082402
(
2024
).
5.
J.
Sødequist
and
T.
Olsen
, “
Two-dimensional altermagnets from high throughput computational screening: Symmetry requirements, chiral magnons, and spin-orbit effects
,”
Appl. Phys. Lett.
124
,
182409
(
2024
).
6.
Y.
Kawamoto
,
T.
Kikkawa
,
M.
Kawamata
,
Y.
Umemoto
,
A. G.
Manning
,
K. C.
Rule
,
K.
Ikeuchi
,
K.
Kamazawa
et al, “
Understanding spin currents from magnon dispersion and polarization: Spin-Seebeck effect and neutron scattering study on Tb3Fe5O12
,”
Appl. Phys. Lett.
124
,
132406
(
2024
).
7.
K.-K.
Wu
,
H.-M.
Lee
,
J.
Xu
,
P.-Y.
Yang
,
C. L.
Chien
,
S.-Y.
Huang
, and
D.
Qu
, “
Magnon spin current from a non-collinear magnetic phase in a compensated rare earth ferrimagnet
,”
Appl. Phys. Lett.
124
,
102407
(
2024
).
8.
Z.
Chen
,
J.
Rao
,
K. X.
Zhao
,
F.
Yang
,
C. X.
Wang
,
B.
Yao
, and
W.
Lu
, “
Manipulating the nonreciprocal microwave transmission by using a pump-induced magnon mode
,”
Appl. Phys. Lett.
125
,
042403
(
2024
).
9.
J. K. W.-B.
Wu
,
J.
Przewoźnik
,
C.
Kapusta
,
I.
Svito
,
T. H.
Nguyen
,
K. T.
Do
,
D. T.
Tran
et al, “
The enhancement of low-temperature excitation of magnons via interlayer exchange coupling in perpendicularly magnetized [Co/Pd] multilayers
,”
Appl. Phys. Lett.
124
,
192407
(
2024
).
10.
U.
Makartsou
,
M.
Gołębiewski
,
U.
Guzowska
,
A.
Stognij
,
R.
Gieniusz
, and
M.
Krawczyk
, “
Spin-wave self-imaging: Experimental and numerical demonstration of caustic and Talbot-like diffraction patterns
,”
Appl. Phys. Lett.
124
,
192406
(
2024
).
11.
R. V.
Ovcharov
,
M.
Hamdi
,
B. A.
Ivanov
,
J.
Åkerman
, and
R. S.
Khymyn
, “
Antiferromagnetic droplet soliton driven by spin current
,”
Appl. Phys. Lett.
124
,
172406
(
2024
).
12.
A.
Shadman
and
J.-G.
Zhu
, “
Excitation and dynamics of spin solitons in chiral magnetization configuration
,”
Appl. Phys. Lett.
124
,
172404
(
2024
).
13.
X.
Ge
,
P.
Yan
,
W.
Luo
,
S.
Liang
, and
Y.
Zhang
, “
Terahertz magnon excitation in antiferromagnetic domain walls based on mass-energy equivalence
,”
Appl. Phys. Lett.
124
,
162405
(
2024
).
14.
L.
Liu
,
J.
Ye
,
H.
Yang
,
L.
Lin
, and
H.
An
, “
Tunable anomalous Hall effect in Pt/ferrimagnetic insulator bilayer
,”
Appl. Phys. Lett.
124
,
132409
(
2024
).
15.
S. A.
Odintsov
,
S. E.
Sheshukova
,
S. A.
Nikitov
,
F. Y.
Ogrin
, and
A. V.
Sadovnikov
, “
Nonreciprocal magnonic directional coupler based on metal-coated YIG adjacent stripes
,”
Appl. Phys. Lett.
124
,
112408
(
2024
).
16.
S.-I.
Shamoto
,
M.
Akatsu
,
L.-J.
Chang
,
Y.
Nemoto
, and
J. I.
Ieda
, “
Inelastic neutron scattering study of magnon excitation by ultrasound injection in yttrium iron garnet
,”
Appl. Phys. Lett.
124
,
112402
(
2024
).
17.
D.
Breitbach
,
M.
Bechberger
,
B.
Heinz
,
A.
Hamadeh
,
J.
Maskill
,
K. O.
Levchenko
,
B.
Lägel
,
C.
Dubs
et al, “
Nonlinear erasing of propagating spin-wave pulses in thin-film Ga:YIG
,”
Appl. Phys. Lett.
124
,
092405
(
2024
).
18.
D.-Q.
To
,
A.
Rai
,
J. M. O.
Zide
,
S.
Law
,
J. Q.
Xiao
,
M. B.
Jungfleisch
, and
M. F.
Doty
, “
Hybridized magnonic materials for THz frequency applications
,”
Appl. Phys. Lett.
124
,
082405
(
2024
).
19.
X.
Li
,
Y.
Yao
,
F.
Ma
,
J.
Wang
, and
G.
Chai
, “
Mode transformation of dynamic spin wave well modes in the magnetic stripes
,”
Appl. Phys. Lett.
124
,
062408
(
2024
).
20.
Y.
Wang
,
X.
Xu
,
L.
Zhang
,
L.
Jin
, and
H.
Zhang
, “
Frequency-selective coherent propagating spin waves induced by localized perpendicular magnetic anisotropy nanofilm stack
,”
Appl. Phys. Lett.
124
,
063407
(
2024
).
21.
Z.-K.
Xie
,
J.-W.
Cai
,
Z.-H.
Cheng
, and
W.
He
, “
Coherent excitation of spin waves in synthetic antiferromagnets by subpicosecond spin-transfer-torque
,”
Appl. Phys. Lett.
124
,
042406
(
2024
).
22.
Z.-X.
Li
,
X.
Liu
,
Z.-M.
Yan
,
X.-G.
Wang
, and
G.-H.
Guo
, “
Realizing polarization-dependent unidirectional magnon channel in antiferromagnetic domain wall
,”
Appl. Phys. Lett.
124
,
032401
(
2024
).
23.
S.
Zhou
,
C.
Zheng
,
C.
Wang
, and
Y.
Liu
, “
Electric-field control of spin-wave packets excitations
,”
Appl. Phys. Lett.
124
,
022401
(
2024
).
24.
S.
Ke
,
W.-K.
Lou
,
Y.-M.
Li
, and
K.
Chang
, “
Topological antichiral edge states and one-way bulk states in patterned ferromagnetic thin films
,”
Appl. Phys. Lett.
123
,
242404
(
2023
).
25.
J.
de Rojas
,
D.
Atkinson
, and
A. O.
Adeyeye
, “
Tuning magnon spectra via interlayer coupling in pseudo-3D nanostructured artificial spin ice arrays
,”
Appl. Phys. Lett.
123
,
232407
(
2023
).
26.
C.
Chen
,
C.
Zheng
,
J.
Zhang
, and
Y.
Liu
, “
Chirality reversal of resonant modes in GdFe ferrimagnets
,”
Appl. Phys. Lett.
123
,
212403
(
2023
).
27.
M. A.
Morozova
,
O. V.
Matveev
,
S. A.
Gusev
,
N. S.
Gusev
,
D. V.
Romanenko
, and
S. A.
Nikitov
, “
Laser-induced Bragg resonances in ferrit/semiconductor heterostructure
,”
Appl. Phys. Lett.
123
,
202406
(
2023
).
28.
Y.
Jin
,
Y.
Zhao
,
B.
Liang
, and
C.
Jiang
, “
Excitation and modulation of exchange spin waves in CoFeB films
,”
Appl. Phys. Lett.
123
,
172402
(
2023
).
29.
A. A.
Martyshkin
,
S. E.
Sheshukova
, and
A. V.
Sadovnikov
, “
Nonlinear magnonic coupler using backpropagating surface spin waves
,”
Appl. Phys. Lett.
124
,
092413
(
2024
).
30.
V. K.
Sakharov
,
Y. V.
Khivintsev
,
Y. V.
Nikulin
,
A. S.
Dzhumaliev
,
A. V.
Kozhevnikov
, and
Y. A.
Filimonov
, “
Pass bands formation in YIG film with periodic metal grating
,”
Appl. Phys. Lett.
123
,
252403
(
2023
).
31.
A. A.
Grachev
,
S. E.
Sheshukova
, and
A. V.
Sadovnikov
, “
Strain-induced multi-band spin-wave logic gate based on alligator-type magnonic crystal/PZT structure
,”
Appl. Phys. Lett.
124
,
162406
(
2024
).
32.
D.
Wuhrer
,
N.
Rohling
, and
W.
Belzig
, “
Dipole–dipole-interaction-induced entanglement between two-dimensional ferromagnets
,”
Appl. Phys. Lett.
125
,
022404
(
2024
).
33.
D.
Narducci
,
X.
Wu
,
I.
Boventer
,
J. D.
Boeck
,
A.
Anane
,
P.
Bortolotti
,
C.
Adelmann
, and
F.
Ciubotaru
, “
Magnetoelectric coupling in Ba:Pb(Zr,Ti)O3/Co40Fe40B20 nanoscale waveguides studied by propagating spin-wave spectroscopy
,”
Appl. Phys. Lett.
124
,
182408
(
2024
).
34.
Y.
Kunz
,
M.
Küß
,
M.
Schneider
,
M.
Geilen
,
P.
Pirro
,
M.
Albrecht
, and
M.
Weiler
, “
Coherent surface acoustic wave–spin wave interactions detected by micro-focused Brillouin light scattering spectroscopy
,”
Appl. Phys. Lett.
124
,
152403
(
2024
).
35.
B. W.
Zingsem
,
T.
Feggeler
,
D.
Spoddig
,
R.
Meckenstock
,
M.
Farle
, and
M.
Winklhofer
, “
Reciprocity relations in a biologically inspired nanomagnonic system with dipolar coupling
,”
Appl. Phys. Lett.
124
,
132405
(
2024
).
36.
Z.-X.
Lin
and
S.
Zhang
, “
Topological magnon–polaron transport in a bilayer van der Waals magnet
,”
Appl. Phys. Lett.
124
,
132402
(
2024
).
37.
O. J.
Barker
,
A.
Mohammadi-Motlagh
,
A. J.
Wright
,
R.
Batty
,
H.
Finch
,
A.
Vezzoli
,
P. S.
Keatley
, and
L.
O'Brien
, “
Thermal nanoconversion of ferromagnetic nanoislands
,”
Appl. Phys. Lett.
124
,
112411
(
2024
).
38.
H.
Xiong
, “
Controllable switching of the magnonic excitation based on the magnetostrictive effect
,”
Appl. Phys. Lett.
124
,
112403
(
2024
).
39.
W.
Chen
,
N.
Zhao
,
Y.
Huang
,
X.
Zeng
,
K.
Zhang
,
J.
Zhou
, and
X.
Xu
, “
Magnon–phonon coupling modulation via dimensional reduction in thin antiferromagnet MnPSe3 nanoribbons
,”
Appl. Phys. Lett.
124
,
112406
(
2024
).
40.
T. V.
Bogdanova
,
A. A.
Meshcheryakov
,
D. V.
Kalyabin
,
A. B.
Khutieva
,
A. V.
Sadovnikov
,
A. R.
Safin
, and
S. A.
Nikitov
, “
Influence of mechanical strains on the antiferromagnetic resonance modes of bulk α-Fe2O3
,”
Appl. Phys. Lett.
124
,
092410
(
2024
).
41.
X.
Wang
,
S.
Yuan
,
C.
Sui
,
Y.
Wang
, and
C.
Jia
, “
Realization of Hadamard gate with twisted magnon modes in synthetic antiferromagnets
,”
Appl. Phys. Lett.
124
,
072405
(
2024
).
42.
J. T.
Hou
,
C.-T.
Chou
,
J.
Han
,
Y.
Fan
, and
L.
Liu
, “
Electrical manipulation of dissipation in microwave photon–magnon hybrid system through the spin Hall effect
,”
Appl. Phys. Lett.
124
,
072401
(
2024
).
43.
O.
Borovkova
,
A.
Kolosvetov
,
A.
Kalish
,
A.
Chernov
, and
V.
Belotelov
, “
Patterned magnetophotonic crystal for all-optical magnetization precession generation
,”
Appl. Phys. Lett.
124
,
042402
(
2024
).
44.
T.
Chiba
,
T.
Komine
, and
T.
Aono
, “
Ultrastrong-coupled magnon–polariton in a dynamical inductor based on magnetic-insulator/topological-insulator bilayers
,”
Appl. Phys. Lett.
124
,
12402
(
2024
).
45.
Z.
Li
,
J.
Sun
, and
F.
Ma
, “
Floquet engineering of selective magnon–magnon coupling in synthetic antiferromagnets
,”
Appl. Phys. Lett.
123
,
232406
(
2023
).
46.
D.
Zheng
,
M.
Tang
,
J.
Xu
,
C.
Liu
,
Y.
Li
,
A.
Chen
,
H.
Algaidi
,
F.
Alsayafi
et al, “
Temperature-dependent magnon torque in SrIrO3/NiO/ferromagnetic multilayers
,”
Appl. Phys. Lett.
124
,
102406
(
2024
).
47.
J. T.
Mäkinen
,
S.
Autti
, and
V. B.
Eltsov
, “
Magnon Bose–Einstein condensates: From time crystals and quantum chromodynamics to vortex sensing and cosmology
,”
Appl. Phys. Lett.
124
,
100502
(
2024
).
48.
M. R.
Schweizer
,
F.
Kühn
,
V. S.
L'vov
,
A.
Pomyalov
,
G.
von Freymann
,
B.
Hillebrands
, and
A. A.
Serga
, “
Local temperature control of magnon frequency and direction of supercurrents in a magnon Bose–Einstein condensate
,”
Appl. Phys. Lett.
124
,
092402
(
2024
).
49.
Z.-X.
Liu
, “
Dissipative coupling induced UWB magnonic frequency comb generation
,”
Appl. Phys. Lett.
124
,
032403
(
2024
).
50.
P. M.
Gunnink
,
T.
Ludwig
, and
R. A.
Duine
, “
Magnon spin capacitor
,”
Appl. Phys. Lett.
124
,
182404
(
2024
).
51.
X.
Ge
,
R.
Verba
,
P.
Pirro
,
A. V.
Chumak
, and
Q.
Wang
, “
Nanoscaled magnon transistor based on stimulated three-magnon splitting
,”
Appl. Phys. Lett.
124
,
122413
(
2024
).
52.
M. S.
Swyt
,
L.
Compton
,
A.
Reyes-Almanza
,
C. L. O.
Romero
,
G.
Pirruccio
,
H. J. J.
Liu
, and
K. S.
Buchanan
, “
Magnonic notch filter based on spin wave caustic beams
,”
Appl. Phys. Lett.
124
,
112410
(
2024
).
53.
M.
Kim
,
C.
Zhang
,
C.
Lu
, and
C.-M.
Hu
, “
Low phase noise microwave oscillator based on gain driven polariton
,”
Appl. Phys. Lett.
124
,
114103
(
2024
).
54.
J.
Klíma
,
O.
Wojewoda
,
V.
Roučka
,
T.
Molnár
,
J.
Holobrádek
, and
M.
Urbánek
, “
Zero-field spin wave turns
,”
Appl. Phys. Lett.
124
,
112404
(
2024
).
55.
V. H.
González
,
A.
Litvinenko
,
R.
Khymyn
, and
J.
Åkerman
, “
Global biasing using a hardware-based artificial Zeeman term in spinwave Ising machines
,”
Appl. Phys. Lett.
124
,
092409
(
2024
).
56.
A. B.
Ustinov
,
R. V.
Haponchyk
, and
M.
Kostylev
, “
A current-controlled magnonic reservoir for physical reservoir computing
,”
Appl. Phys. Lett.
124
,
042405
(
2024
).
57.
M. H.
Waseem
and
A. D.
Karenowska
, “
String diagrams for wave-based computation
,”
Appl. Phys. Lett.
123
,
242402
(
2023
).
58.
Y.-J.
Chen
,
T.-H.
Chuang
,
J.-P.
Hanke
,
Y.
Mokrousov
,
S.
Blügel
,
C. M.
Schneider
, and
C.
Tusche
, “
Magnons in a two-dimensional Weyl magnet
,”
Appl. Phys. Lett.
124
,
093105
(
2024
).