# Ferromagnetism

• Article
| Open Access

### Thermally active nanoparticle clusters enslaved by engineered domain wall traps

Assembling nanoparticles on surfaces has great technological potential. Here, Tierno et al demonstrate the confinement of magnetic nanoparticles in traps created by magnetic domain walls. The magnetic gradient and location of the domain walls can be finely tuned, allowing for precise control of the constituent nanoparticles.

• Pietro Tierno
• , Tom H. Johansen
•  & Arthur V. Straube
• Article
| Open Access

### Magnetic skyrmion braids

Skyrmions are topological two-dimensional spin textures that in three-dimensional systems resemble strings or tubes. Here, using transmission electron microscopy Zheng et al observe the braiding of skyrmion strings in FeGe and predict this phenomenon for a large family of magnets.

• Fengshan Zheng
• , Filipp N. Rybakov
•  & Rafal E. Dunin-Borkowski
• Article
| Open Access

### Subpicosecond metamagnetic phase transition in FeRh driven by non-equilibrium electron dynamics

In FeRh, it is possible to optically drive a phase transition between ferromagnetic (FM) and anti-ferromagnetic (AFM) ordering. Here, using a combination of photoelectron spectroscopy and ab-initio calculations, the authors demonstrate the existence of a transient intermediate phase, explaining the delayed appearance of the FM phase.

• Federico Pressacco
• , Davide Sangalli
•  & Fausto Sirotti
• Article
| Open Access

### Competing correlated states and abundant orbital magnetism in twisted monolayer-bilayer graphene

Twisted monolayer-bilayer graphene is an attractive platform to study the interplay between topology, magnetism and correlations in the flat bands. Here, using electrical transport measurements, the authors uncover a rich correlated phase diagram and identify a new insulating state that can be explained by intervalley coherence with broken time reversal symmetry.

• Minhao He
• , Ya-Hui Zhang
•  & Matthew Yankowitz
• Article
| Open Access

### Ruderman–Kittel–Kasuya–Yosida-type interfacial Dzyaloshinskii–Moriya interaction in heavy metal/ferromagnet heterostructures

The mechanism of the interfacial Dzyaloshinskii-Moriya interaction in heavy metal-ferromagnet heterostructures is debated. Here, the authors show the oscillating behaviour of the interaction as a function of the MgO spacer layer thickness, supporting the interlayer exchange coupling mechanism of the Ruderman-Kittel-Kasuya-Yosida type.

• Taehyun Kim
• , In Ho Cha
•  & Young Keun Kim
• Article
| Open Access

### Magnetic charge propagation upon a 3D artificial spin-ice

Two-dimensional artificial spin-ice systems have been studied for over 15 years but do not capture the detailed geometry of their bulk counterparts. Here, the authors fabricate a three-dimensional artificial spin-ice and show that the surface termination plays a crucial role in dictating the magnetic charge transport.

• A. May
• , M. Saccone
• Article
| Open Access

### Dipolar-stabilized first and second-order antiskyrmions in ferrimagnetic multilayers

Antiskyrmions are topological spin textures with negative vorticity. Like skyrmions, they have considerable technological promise, but have only been stabilised in Heusler compounds. Here, Heigl et al. succeed in stabilising first and second order antiskyrmions in a new class of materials.

• Michael Heigl
• , Sabri Koraltan
•  & Manfred Albrecht
• Article
| Open Access

### Reconfigurable magnonic mode-hybridisation and spectral control in a bicomponent artificial spin ice

Reconfigurable magnonic crystals (RMC), comprising nano-patterned arrays of magnetic elements, can host a wide variety of spectrally-distinct microstates with great potential for functional magnonics. Here, Gartside et al, present an RMC with four distinct microstates, possessing diverse magnonic properties and exhibiting reconfigurable magnon mode hybridisation.

• Jack C. Gartside
• , Alex Vanstone
•  & Will R. Branford
• Article
| Open Access

### Interferometric control of magnon-induced nearly perfect absorption in cavity magnonics

Perfect absorption can be obtained for a single port device, or a device with multiple incident beams, but for multiport devices, the absorption is limited to around 50%. In this work, Rao et al. overcome this limitation, demonstrating near perfect absorption in a two port cavity magnon system.

• J. W. Rao
• , P. C. Xu
•  & C.-M. Hu
• Article
| Open Access

### Microwave resonances of magnetic skyrmions in thin film multilayers

The dynamic properties of Néel skyrmions in magnetic thin films have remained elusive. Here, the authors report distinct resonances in Ir/Fe/Co/Pt heterostructures whose frequencies vary with the skyrmion configuration and multilayer architecture, thus opening a path to microwave applications.

• Bhartendu Satywali
• , Volodymyr P. Kravchuk
•  & Christos Panagopoulos
• Article
| Open Access

### Embedding atomic cobalt into graphene lattices to activate room-temperature ferromagnetism

Graphene has shown incredible promise as ideal material for numerous fields; however its use in spintronics has been hampered by the lack of intrinsic magnetism. Here, Hu et al succeed in embedding Cobalt in the graphene lattice, creating robust room-temperature ferromagnetism.

• Wei Hu
• , Chao Wang
•  & Wensheng Yan
• Article
| Open Access

### High-efficiency magnetic refrigeration using holmium

Magnetic refrigeration offers a promising alternative to gas cycle cooling; however, it is typically hampered by the need for large magnetic fields. Here, the authors demonstrate that holmium can exhibit a large magnetic caloric effect while requiring only small magnetic fields.

•  & Hiroaki Mamiya
• Article
| Open Access

### Real-time Hall-effect detection of current-induced magnetization dynamics in ferrimagnets

Measuring real time magnetization dynamics resulting from Hall effects is hard due to the small signal size. Here Sala et al demonstrate a method of performing Hall resistance measurements with sub-ns resolution, and use it to investigate the switching of GdFeCo dots induced by spin-orbit torques.

• G. Sala
• , V. Krizakova
•  & P. Gambardella
• Article
| Open Access

### Uncooled sub-GHz spin bolometer driven by auto-oscillation

Goto et al present a bolometer based around the heat generation in magnetic tunnel junctions under auto-oscillation conditions. Unlike superconducting bolometers, the presented device operates at room temperature and sub-GHz frequencies, opening possibilities for use in microwave devices.

• Minori Goto
•  & Yoshishige Suzuki
• Article
| Open Access

### Interface-induced sign reversal of the anomalous Hall effect in magnetic topological insulator heterostructures

Berry curvature connects to exotic electronic phases hence it provides important insights to understand quantum materials. Here, the authors report sign change of the anomalous Hall effect resulted from Berry curvature change at the interface of a topological insulator/magnetic topological insulator heterostructure.

• Fei Wang
• , Xuepeng Wang
•  & Cui-Zu Chang
• Article
| Open Access

### Faster chiral versus collinear magnetic order recovery after optical excitation revealed by femtosecond XUV scattering

Chiral spin structures have great promise for future information processing applications, however little is known about their ultrafast dynamics. In this experimental study, the authors use femtosecond temporal evolution to observe the fast recovery of chiral magnetic order.

• Nico Kerber
• , Dmitriy Ksenzov
•  & Christian Gutt
• Article
| Open Access

### Site-specific spectroscopic measurement of spin and charge in (LuFeO3)m/(LuFe2O4)1 multiferroic superlattices

Understanding the inner workings of complex magnetoelectric multiferroics remains a challenge, as macroscopic techniques characterize average responses rather than the role of individual iron centers. Here, the authors reveal the origin of high-temperature magnetism in multiferroic superlattices.

• Shiyu Fan
• , Hena Das
•  & Janice L. Musfeldt
• Article
| Open Access

### A three-order-parameter bistable magnetoelectric multiferroic metal

A room temperature single-phase multiferroic with large and strongly coupled polarization and magnetization is a long-sought goal in multiferroics research. Here, the authors predict a promising candidate, layered-perovskite metal Bi5Mn5O17, which is a ferromagnet, ferroelectric, and ferrotoroid.

• Andrea Urru
• , Francesco Ricci
•  & Vincenzo Fiorentini
• Article
| Open Access

### Giant voltage-induced modification of magnetism in micron-scale ferromagnetic metals by hydrogen charging

“Electric field control of ferromagnetism is typically limited by screening, and is restricted to the first few layers of metals. Here the authors overcome this limitation via the absorption of hydrogen into metal structure, demonstrating voltage control of magnetic properties of micron-scale SmCo5.”

• Xinglong Ye
• , Harish K. Singh
•  & Robert Kruk
• Article
| Open Access

### Fabrication of a novel magnetic topological heterostructure and temperature evolution of its massive Dirac cone

Magnetic topological heterostructures are promising devices to manipulate emergent quantum effects. Here, Hirahara et al. fabricate a novel magnetic topological heterostructure with a massive Dirac cone which becomes a massless one tuned by temperature.

• T. Hirahara
• , M. M. Otrokov
•  & E. V. Chulkov
• Article
| Open Access

### Resonant thermal energy transfer to magnons in a ferromagnetic nanolayer

Most of the energy harvesting principles are realized in heated-continuously systems. Here, the authors present a concept of high-frequency energy harvesting where the dissipated heat in a sample excites resonant magnons in a ferromagnetic metal layer.

• Michal Kobecki
• , Alexey V. Scherbakov
•  & Manfred Bayer
• Article
| Open Access

### Distinct magneto-Raman signatures of spin-flip phase transitions in CrI3

Thin samples CrI3 exhibit a phase transition under an applied magnetic field from layered antiferromagnetism to ferromagnetism. Here the authors observe an associated abrupt change in the magneto-Raman spectra, illustrating the sensitivity of Raman spectra to magnetic ordering.

• Amber McCreary
• , Thuc T. Mai
•  & Angela R. Hight Walker
• Article
| Open Access

### Unconventional Hund metal in a weak itinerant ferromagnet

The rich magnetic phase behaviour of MnSi reflects the complexity of the physics underlying itinerant ferromagnetism. Here the authors present evidence that MnSi is strongly influenced by Hund’s coupling effects, suggesting a broader class of materials may fall into the class of Hund metals.

• Xiang Chen
• , Igor Krivenko
•  & Stephen D. Wilson
• Article
| Open Access

### Probing the pinning strength of magnetic vortex cores with sub-nanometer resolution

Magnetic vortices such as skyrmions are promising for spintronic applications, however, little is known about the pinning effects strongly influencing their dynamics. Here, the authors map the interaction potential between defects and vortex cores down to the sub-nanometer scale enabling the better control of these magnetic textures.

• Christian Holl
• , Marvin Knol
•  & Markus Morgenstern
• Article
| Open Access

### Enabling room temperature ferromagnetism in monolayer MoS2 via in situ iron-doping

Ferromagnetism with a Curie temperature above room temperature in 2D materials is highly desirable for practical spintronics applications. Here, the authors demonstrate such phenomenon in monolayer MoS2 via in situ iron-doping and measured local magnetic field strength up to 0.5 ± 0.1 mT.

• Shichen Fu
• , Kyungnam Kang
•  & Eui-Hyeok Yang
• Article
| Open Access

### Direct evidence of spatial stability of Bose-Einstein condensate of magnons

Little is known about the underlying mechanism responsible for the spatial stability of magnon Bose-Einstein condensates. Here experimental evidence is provided for a repulsive interaction of magnons in the condensate resulting in its stabilization.

• I. V. Borisenko
• , B. Divinskiy
•  & S. O. Demokritov
• Article
| Open Access

### Ferromagnetic quasi-atomic electrons in two-dimensional electride

Ferromagnetic quasi-atomic behavior of interstitial anionic electrons (IAEs) in practical electrides is yet to be discovered experimentally. Here, the authors reveal that IAEs in two-dimensional electride [Gd2C]²+2e- behave as magnetic elements with their own magnetic moment.

• Seung Yong Lee
• , Jae-Yeol Hwang
•  & Sung Wng Kim
• Article
| Open Access

### Optical spin-orbit torque in heavy metal-ferromagnet heterostructures

It is known that torques can be exerted on spins in a ferromagnet (FM) layer when an in-plane electric current is injected into a heavy metal (HM) layer in contact with the FM layer. Here, the authors demonstrate that torques can be generated without the current injection by shining instead circularly polarized light on the HM.

• Gyung-Min Choi
• , Jung Hyun Oh
•  & Hyun-Woo Lee
• Article
| Open Access

### Efficient wavelength conversion of exchange magnons below 100 nm by magnetic coplanar waveguides

Magnons - collective excitations of electron spins - promise compact and fast electronics. However, the generation of short wave magnons is still quite challenging. Here, the authors demonstrate that by introducing a ferromagnetic layer, conventional coplanar waveguides can be used to efficiently generate such magnons.

• Ping Che
• , Korbinian Baumgaertl
•  & Dirk Grundler
• Article
| Open Access

### Emergent electric field control of phase transformation in oxide superlattices

Many complex oxides already have rich functional behavior but oxide heterostructures can exhibit new emergent properties. Yi et al. show that LSMO/SIO superlattices have a reversible electric-field-controlled structural phase transition that is not present in the constituent materials.

• Di Yi
• , Yujia Wang
•  & Yuri Suzuki
• Article
| Open Access

### Optical inter-site spin transfer probed by energy and spin-resolved transient absorption spectroscopy

Optically driven spin transfer is the fastest process to manipulate magnetism. Here, the authors show that this process emerges as the dominant mechanism in femtosecond spin dynamics enabling to the engineering of functional magnetic systems for future all optical technologies.

• Felix Willems
• , Clemens von Korff Schmising
•  & Stefan Eisebitt
• Article
| Open Access

### Exchange biased anomalous Hall effect driven by frustration in a magnetic kagome lattice

The Weyl semimetal Co\$\$_{3}\$\$${}_{3}$Sn\$\$_{2}\$\$${}_{2}$S\$\$_{2}\$\$${}_{2}$ exhibits a combination of magnetic ordering with a large anomalous Hall effect. Lachman et al. find an intrinsic exchange bias of this anomalous Hall effect and attribute it to the coexistence of ferromagnetism and spin glass behaviour.

• Ella Lachman
• , Ryan A. Murphy
•  & James G. Analytis
• Article
| Open Access

### Topological–chiral magnetic interactions driven by emergent orbital magnetism

The motion of electrons in a complex magnetic background may generate novel magnetic interactions. Here, Grytsiuk et al. report that a peculiar orbital motion of electrons in response to a non-coplanarity of neighbouring spins leads to a topological orbital moment, which further gives rise to a new class of magnetic interactions.

• S. Grytsiuk
• , J.-P. Hanke
•  & S. Blügel
• Article
| Open Access

### Reversible manipulation of the magnetic state in SrRuO3 through electric-field controlled proton evolution

Ionic substitution is a useful way to manipulate structural, electronic, magnetic phase transitions in strongly correlated materials. Here, the authors report electric-field controlled protonation in SrRuO3, resulting in a large structural expansion and a ferromagnetic-to-paramagnetic phase transition.

• Zhuolu Li
• , Shengchun Shen
•  & Pu Yu
• Article
| Open Access

### Realization of Lieb lattice in covalent-organic frameworks with tunable topology and magnetism

Although artificial Lieb lattices have been recently synthesized, the realization of a Lieb lattice in a real material is still challenging. Here the authors use tight-binding and first principle calculations to predict tunable topology and magnetism in recently discovered two-dimensional covalent-organic frameworks.

• Bin Cui
• , Xingwen Zheng
•  & Bing Huang
• Article
| Open Access

### Theory of correlated insulating behaviour and spin-triplet superconductivity in twisted double bilayer graphene

Twisted bilayer graphene exhibits correlated electronic phases and superconductivity, but its precise nature is under debate. Here, Lee and Khalaf et al. study a twisted double bilayer graphene, where ferromagnetic insulator and spin triplet superconducting phases can be stabilized.

• Jong Yeon Lee
• , Eslam Khalaf
•  & Ashvin Vishwanath
• Article
| Open Access

### Femtosecond X-ray induced changes of the electronic and magnetic response of solids from electron redistribution

X-ray free electron lasers allow for studying the interaction of magnetic materials with intense X-rays beyond a linear response regime. Here, the authors demonstrate the onset of X-ray induced ultrafast demagnetization in Co/Pd multilayers via a redistribution of valence electrons on timescales shorter than 40 fs.

• Daniel J. Higley
• , Alex H. Reid
•  & Joachim Stöhr
• Article
| Open Access

### de Haas-van Alphen effect of correlated Dirac states in kagome metal Fe3Sn2

The kagome lattice is increasingly known as a host for correlated topological electronic states. Here, Ye et al. report quantum de Haas-van Alphen oscillations of a ferromagnetic kagome material Fe3Sn2, where bulk electronic Dirac fermions are found to be modulated by rotation of the magnetic moment.

• Linda Ye
• , Mun K. Chan
•  & Joseph G. Checkelsky
• Article
| Open Access

### Mixed topological semimetals driven by orbital complexity in two-dimensional ferromagnets

Whether topological semimetal states can emerge in two-dimensional magnetic materials remains less understood. Here, Niu and Hanke et al. propose the concepts of mixed Weyl and nodal-line semimetallic phases by including the magnetization direction into the topological analysis in two-dimensional ferromagnets.

• Chengwang Niu
• , Jan-Philipp Hanke
•  & Yuriy Mokrousov
• Article
| Open Access

### Analogue of dynamic Hall effect in cavity magnon polariton system and coherently controlled logic device

Exploring photon-polariton interactions advances not only the understanding of polariton dynamics but also the modern technologies. Here the authors take advantage of strong coupled magnons and microwave photons in a cross-cavity to achieve tunable cavity magnon polariton transport which can be potentially applied as logic devices.

• J. W. Rao
• , S. Kaur
•  & C.-M. Hu
• Article
| Open Access

### Low voltage control of exchange coupling in a ferromagnet-semiconductor quantum well hybrid structure

Manipulating magnetic orders by electric fields promises energy efficient spintronic applications. Here the authors demonstrate electrical control of s-p exchange interaction in a ferromagnet-semiconductor quantum well structure due to the phononic ac Stark effect.

• V. L. Korenev
• , I. V. Kalitukha
•  & M. Bayer
• Article
| Open Access

### Orbital-flop Induced Magnetoresistance Anisotropy in Rare Earth Monopnictide CeSb

The orbital degree of freedom can be as important as the charge and spin of the electron to the electronic phenomena. Here the authors show additional minimum in the angle-dependent magnetoresistance (MR) for the low temperature high magnetic field driven ferromagnetic state in CeSb which indicates the orbital flop induced MR anisotropy.

• Jing Xu
• , Fengcheng Wu
•  & Wai-Kwong Kwok
• Article
| Open Access

### Strongly coupled magnon–phonon dynamics in a single nanomagnet

Exploring the magnon and phonon coupling may enable high efficiency magnonic applications. Here the authors show the observation, understanding and control of the magnon–phonon interaction by studying the magneto-acoustic resonance modes of a single thin-film Ni nanomagnet.

• Cassidy Berk
• , Mike Jaris
•  & Holger Schmidt
• Article
| Open Access

### A Lieb-like lattice in a covalent-organic framework and its Stoner ferromagnetism

While ferromagnetism has been observed in an sp2 covalent-organic framework, its origin remains unclear. Here, by first-principle and tight-binding calculations, the authors identify the Lieb-lattice-like feature of the two-dimensional covalent-organic material and the Stoner mechanism responsible for its magnetic behavior.

• Wei Jiang
• , Huaqing Huang
•  & Feng Liu
• Article
| Open Access

### Ferromagnetism above 1000 K in a highly cation-ordered double-perovskite insulator Sr3OsO6

Pursuing high Curie temperature magnetic insulators has been one of the extensively studied subjects due to their wide appeal for spintronic applications. Here the authors experimentally and theoretically demonstrate a record high Curie temperature over 1000 K in B-site ordered double-perovskite, Sr3OsO6.

• Yuki K. Wakabayashi
• , Yoshiharu Krockenberger
•  & Hideki Yamamoto
• Article
| Open Access

### Kink far below the Fermi level reveals new electron-magnon scattering channel in Fe

The conduction electron and magnon interactions are essential for the understanding and development of spintronics and superconductivity. Here the authors show a deep binding energy kink in spin-resolved photoemission spectra which is understood as a signature the many-body spin flip excitation in Fe single crystal thin film.

• E. Młyńczak
• , M. C. T. D. Müller
•  & C. M. Schneider
• Article
| Open Access

### Low-loss YIG-based magnonic crystals with large tunable bandgaps

Control of spin wave transport in magnonic crystals is vital for magnonic devices. Here the authors show low-loss spin-wave manipulation in nanometer thick magnonic crystals of discrete YIG stripes separated by air or CoFeB filled grooves exhibiting tunable bandgaps of 50–200 MHz.

• Huajun Qin
• , Gert-Jan Both
•  & Sebastiaan van Dijken
• Article
| Open Access

### Pressure tuning of charge ordering in iron oxide

The charge order transition of commonly known magnetite has only recently been unraveled. Here, the measurement of the low-temperature high-pressure phase diagram of a related material (Fe4O5) elucidates the interplay of average oxidation state and charge-ordering phenomena in the iron oxide family.

• Sergey V. Ovsyannikov
• , Maxim Bykov
•  & Leonid S. Dubrovinsky
• Article
| Open Access

### Nonlocal electron correlations in an itinerant ferromagnet

The consequences of electron-electron interactions are difficult to calculate reliably but this is needed to understand important physical properties such as ferromagnetism. Tusche et al. show that interaction effects in cobalt are nonlocal, presenting a challenge to future theoretical approaches.

• Christian Tusche
• , Martin Ellguth
•  & Jürgen Kirschner
• Article
| Open Access

### Large intrinsic anomalous Hall effect in half-metallic ferromagnet Co3Sn2S2 with magnetic Weyl fermions

The large intrinsic anomalous Hall effect (AHE) in magnetic Weyl semimetals is expected but rarely verified experimentally. Here, Wang et al. report large intrinsic AHE with linear dependence on magnetization in a half-metallic ferromagnet Co3Sn2S2 single crystal with Kagome lattice of Co atoms, arising dominantly from the Weyl fermions.

• Qi Wang
• , Yuanfeng Xu
•  & Hechang Lei