Spintronics is a research field that aims to understand and control spins on the nanoscale and should enable next-generation data storage and manipulation. One technological and scientific key challenge is to stabilize small spin textures and to move them efficiently with high velocities. For a long time, research focused on ferromagnetic materials, but ferromagnets show fundamental limits for speed and size. Here, we circumvent these limits using compensated ferrimagnets. Using ferrimagnetic Pt/GdCo/TaO films with a sizeable Dzyaloshinskii-Moriya interaction, we realize a current-driven domain wall motion with a speed of 1.3 km s near the angular momentum compensation temperature (T) and room-temperature-stable skyrmions with minimum diameters close to 10 nm near the magnetic compensation temperature (T). Both the size and dynamics of the ferrimagnet are in excellent agreement with a simplified effective ferromagnet theory. Our work shows that high-speed, high-density spintronics devices based on current-driven spin textures can be realized using materials in which T and T are close together.

Magnetic oxides exhibit rich fundamental physics 1-4 and technologically desirable properties for spin-based memory, logic and signal transmission [5][6][7] . Recently, spin-orbit-induced spin transport phenomena have been realized in insulating magnetic oxides by using proximate heavy metal layers such as platinum 8-10 . In their metallic ferromagnet counterparts, such interfaces also give rise to a Dzyaloshinskii-Moriya interaction 11-13 that can stabilize homochiral domain walls and skyrmions with efficient current-driven dynamics. However, chiral magnetism in centrosymmetric oxides has not yet been observed. Here we discover chiral magnetism that allows for pure spin-current-driven domain wall motion in the most ubiquitous class of magnetic oxides, ferrimagnetic iron garnets. We show that epitaxial rare-earth iron garnet films with perpendicular magnetic anisotropy exhibit homochiral Néel domain walls that can be propelled faster than 800 m s −1 by spin current from an adjacent platinum layer. We find that, despite the relatively small interfacial Dzyaloshinskii-Moriya interaction, very high velocities can be attained due to the antiferromagnetic spin dynamics associated with ferrimagnetic order.Chiral exchange interactions arise from broken spatial inversion symmetry. Only a limited number of inversion-asymmetric bulk magnetic materials are known [14][15][16] , but engineered interfaces can induce a chiral Dzyaloshinskii-Moriya interaction (DMI) in common centrosymmetric ferromagnets [17][18][19][20] in which topological spin textures would otherwise not be found. So far, most research has focused on metallic ferromagnet/heavy-metal bilayers, in which chiral spin textures can be stabilized by an interfacial DMI at room temperature [21][22][23] . Such systems simultaneously benefit from the large spin Hall effect present in DMI-inducing heavy metals like platinum, which provides a source of pure spin current to manipulate chiral spin textures efficiently 21,24 .Due to their chemical and structural complexity, magnetic oxides exhibit a broader range of exotic and useful properties than metals, and oxide-based spintronics may permit functionalities not otherwise readily achieved 4,5,7 . Insulating magnetic oxides are of particular interest due to their low damping, large magnon diffusion length and the possibility to generate and transmit pure spin currents with minimal dissipation 6,9 . However, the realization of chiral spin textures in magnetic oxides remains a challenge, as few bulk chiral magnetic oxides are known 16 . The interface-induced DMI in centrosymmetric oxides has so far only been studied in conducting oxides at cryogenic temperatures 25-27 using indirect magneto-transport measurements, the interpretation of which can be ambiguous 28,29 .

Magnetic nanoparticles have garnered sustained research interest for their promise in biomedical applications including diagnostic imaging, triggered drug release, cancer hyperthermia, and neural stimulation. Many of these applications make use of heat dissipation by ferrite nanoparticles under alternating magnetic fields, with these fields acting as an externally administered stimulus that is either present or absent, toggling heat dissipation on and off. Here, an extension of this concept, magnetothermal multiplexing is demonstrated, in which exposure to alternating magnetic fields of differing amplitude and frequency can result in selective and independent heating of magnetic nanoparticle ensembles. The differing magnetic coercivity of these particles, empirically characterized by a custom high amplitude alternating current magnetometer, informs the systematic selection of a multiplexed material system. This work culminates in a demonstration of magnetothermal multiplexing for selective remote control of cellular signaling in vitro.

Healthy subjects were recruited to represent a variety of ages, genders and cultural backgrounds. Ethics oversightAll procedures in the in vivo trials were performed in accordance with the experimental protocol approved by the Committee on the Use of Humans as Experimental Subjects of the Massachusetts Institute of Technology (COUHES Protocol 2101000301). The participants gave informed consent.Note that full information on the approval of the study protocol must also be provided in the manuscript.

Recent advancements in wearable technology have improved lifestyle and medical practices, enabling personalized care ranging from fitness tracking, to real-time health monitoring, to predictive sensing. Wearable devices serve as an interface between humans and technology; however, this integration is far from seamless. These devices face various limitations such as size, biocompatibility, and battery constraints wherein batteries are bulky, are expensive, and require regular replacement. On-body energy harvesting presents a promising alternative to battery power by utilizing the human body's continuous generation of energy. This review paper begins with an investigation of contemporary energy harvesting methods, with a deep focus on piezoelectricity. We then highlight the materials, configurations, and structures of such methods for self-powered devices. Here, we propose a novel combination of thin-film composites, kirigami patterns, and auxetic structures to lay the groundwork for an integrated piezoelectric system to monitor and sense. This approach has the potential to maximize energy output by amplifying the piezoelectric effect and manipulating the strain distribution. As a departure from bulky, rigid device design, we explore compositions and microfabrication processes for conformable energy harvesters. We conclude by discussing the limitations of these harvesters and future directions that expand upon current applications for wearable technology. Further exploration of materials, configurations, and structures introduce interdisciplinary applications for such integrated systems. Considering these factors can revolutionize the production and consumption of energy as wearable technology becomes increasingly prevalent in everyday life.