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The electrical control of magnetic properties is a key requirement for the development of spintronic devices. The demonstration that the ferromagnetic phase transition in cobalt can be changed by applying an electric field at room temperature represents a significant step towards devices that can switch magnetism on and off electrically. Electrical control of magnetic properties is crucial for device applicationsin the field of spintronics 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 . Although the magnetic coercivity or anisotropy has been successfully controlled electrically in metals 9 , 15 , 17 as well as in semiconductors 6 , 10 , 11 , 13 , the electrical control of Curie temperature has been realized only in semiconductors at low temperature 4 , 5 , 8 . Here, we demonstrate the room-temperature electrical control of the ferromagnetic phase transition in cobalt, one of the most representative transition-metal ferromagnets. Solid-state field effect devices consisting of a ultrathin cobalt film 21 , 22 covered by a dielectric layer and a gate electrode were fabricated. We prove that the Curie temperature of cobalt can be changed by up to 12 K by applying a gate electric field of about ±2 MV cm −1 . The two-dimensionality of the cobalt film may be relevant to our observations. The demonstrated electric field effect in the ferromagnetic metal at room temperature is a significant step towards realizing future low-power magnetic applications.

Magnetic skyrmions are topologically stable swirling spin textures that appear as particle-like objects in two-dimensional (2D) systems. Here, utilizing scalar magnetic X-ray tomography under applied magnetic fields, we report the direct visualization of the three-dimensional (3D) shape of individual skyrmion strings in the room-temperature skyrmion-hosting non-centrosymmetric compound Mn 1.4 Pt 0.9 Pd 0.1 Sn. Through the tomographic reconstruction of the 3D distribution of the [001] magnetization component on the basis of transmission images taken at various angles, we identify a skyrmion string running through the entire thickness of the sample, as well as various defect structures, such as the interrupted and Y-shaped strings. The observed point defect may represent the Bloch point serving as an emergent magnetic monopole, as proposed theoretically. Our tomographic approach with a tunable magnetic field paves the way for direct visualization of the structural dynamics of individual skyrmion strings in 3D space, which will contribute to a better understanding of the creation, annihilation and transfer of these topological objects. The authors use scalar magnetic X-ray tomography under applied magnetic fields to directly visualize the three-dimensional shape of individual skyrmion strings.

Magnetic domain walls can be controlled through a spin torque, which is usually influenced by extrinsic factors, such as defects, that pin the domain walls to specific configurations. It is now shown that intrinsic pinning conditions can be achieved, which will facilitate the development of efficient information storage devices based on domain wall control. The spin transfer torque is essential for electrical magnetization switching 1 , 2 . When a magnetic domain wall is driven by an electric current through an adiabatic spin torque, the theory predicts a threshold current even for a perfect wire without any extrinsic pinning 3 . The experimental confirmation of this ‘intrinsic pinning’, however, has long been missing. Here, we give evidence that this intrinsic pinning determines the threshold, and thus that the adiabatic spin torque dominates the domain wall motion in a perpendicularly magnetized Co/Ni nanowire. The intrinsic nature manifests itself both in the field-independent threshold current and in the presence of its minimum on tuning the wire width. The demonstrated domain wall motion purely due to the adiabatic spin torque will serve to achieve robust operation and low energy consumption in spintronic devices 5 , 6 , 7 , 8 .

Quantum triangular-lattice antiferromagnets are important prototype systems to investigate numerous phenomena of the geometrical frustration in condensed matter. Apart from highly unusual magnetic properties, they possess a rich phase diagram (ranging from an unfrustrated square lattice to a quantum spin liquid), yet to be confirmed experimentally. One major obstacle in this area of research is the lack of materials with appropriate (ideally tuned) magnetic parameters. Using Cs 2 CuCl 4 as a model system, we demonstrate an alternative approach, where, instead of the chemical composition, the spin Hamiltonian is altered by hydrostatic pressure. The approach combines high-pressure electron spin resonance and r.f. susceptibility measurements, allowing us not only to quasi-continuously tune the exchange parameters, but also to accurately monitor them. Our experiments indicate a substantial increase of the exchange coupling ratio from 0.3 to 0.42 at a pressure of 1.8 GPa, revealing a number of emergent field-induced phases. Theoretical studies of quantum magnetism typically assume idealised lattices with freely tunable parameters, which are difficult to realise experimentally. Zvyagin et al. perform challenging measurements at high pressures to tune and to accurately monitor the exchange parameters of a triangular lattice antiferromagnet.

Controlling the displacement of a magnetic domain wall is potentially useful for information processing in magnetic non-volatile memories and logic devices. A magnetic domain wall can be moved by applying an external magnetic field and/or electric current, and its velocity depends on their magnitudes. Here we show that the applying an electric field can change the velocity of a magnetic domain wall significantly. A field-effect device, consisting of a top-gate electrode, a dielectric insulator layer, and a wire-shaped ferromagnetic Co/Pt thin layer with perpendicular anisotropy, was used to observe it in a finite magnetic field. We found that the application of the electric fields in the range of ±2–3 MV cm −1 can change the magnetic domain wall velocity in its creep regime (10 6 –10 3  m s −1 ) by more than an order of magnitude. This significant change is due to electrical modulation of the energy barrier for the magnetic domain wall motion. The manipulation of domain walls in magnetic materials is attracting interest because of its potential use in memory devices. Chiba et al . demonstrate that the velocity of domain walls in perpendicularly magnetized films can be changed by more than an order of magnitude by applying an electric field.

Single crystals of a two-dimensional quantum spin system with geometric frustration lead to the observation of a ‘pinwheel’ valence-bond ground state. In this case, the distortion of the ideal kagome lattice structure helps to stabilize the quantum spin state. Determining ground states of correlated electron systems is fundamental to understanding unusual phenomena in condensed-matter physics. A difficulty, however, arises in a geometrically frustrated system in which the incompatibility between the global topology of an underlying lattice and local spin interactions gives rise to macroscopically degenerate ground states 1 , potentially prompting the emergence of quantum spin states, such as resonating valence bond 2 , 3 , 4 , 5 , 6 , 7 and valence-bond solid 8 , 9 , 10 , 11 (VBS). Although theoretically proposed to exist in a kagome lattice—one of the most highly frustrated lattices in two dimensions being comprised of corner-sharing triangles—such quantum-fluctuation-induced states have not been observed experimentally. Here we report the first realization of the ‘pinwheel’ VBS ground state in the S =1/2 deformed kagome lattice antiferromagnet Rb 2 Cu 3 SnF 12 (refs  12 , 13 ). In this system, a lattice distortion breaks the translational symmetry of the ideal kagome lattice and stabilizes the VBS state.

The optimal timing of functional endoscopic sinus surgery for odontogenic infections precipitated by retention cysts of the maxillary sinus was investigated. Five adults who underwent functional endoscopic sinus surgery were examined. The root apexes of all teeth that had odontogenic infection protruded into the maxillary sinus. All teeth with odontogenic infections precipitated by the retention cysts had percussion pain, indicating they had periodontitis and pulpitis around the root apex. They were vital teeth, indicating they did not have pulp necrosis. The small area of cyst wall attached to the floor of the maxillary sinus and root apex were left intact. The teeth that had odontogenic infections precipitated by retention cysts continued to be vital with no symptoms. Functional endoscopic sinus surgery should be performed before periodontitis and pulpitis of the root apex progress to ascending pulpitis and pulp necrosis. In other words, functional endoscopic sinus surgery should be performed while the affected tooth is still vital.

Sea straits are known for important sites to modify water-mass properties and transport nutrients through vigorous vertical mixing. The first microstructure measurements ever taken in the Tsugaru Strait, between the Sea of Japan and the Northwest Pacific Ocean, showed elevated turbulent mixing. The turbulent energy dissipation rate was especially enhanced to O (10 −6  W kg −1 ) via an internal hydraulic jump when the throughflow passed over an abrupt sill. Beyond the sill, the associated vertical eddy diffusivity reached O (10 −2  m 2  s −1 ) and the vertical turbulent nitrate flux below the subsurface chlorophyll-a maximum layer was estimated to reach 1 mmolN m −2  day −1 , which could elevate the new production of phytoplankton within the layer. Large vertical velocities exceeding 0.1 m s −1 were also observed near the seafloor of the sill where the flow was hydraulically controlled. A simple advection–diffusion model suggested that the energy dissipation rate of O (10 −5  W kg −1 ) was necessary to reproduce the observed modification of subsurface salinity maximum across the strait. Upwelling and/or vertical straining associated with the internal hydraulic jump is also believed to play an important role in the water-mass modification in the strait and could enhance new primary production for a wide area downstream.

In this report, the magnetic behaviour of bulk and nanoparticles of NiCr 2 O 4 under different applied magnetic fields has been investigated extensively. Nanoparticles of NiCr 2 O 4 (12 nm) were obtained by mechanical milling of polycrystalline powder prepared by polyol method. FC–ZFC measurement of bulk at different applied magnetic fields has revealed the existence of a ferrimagnetic transition around 66 K followed by an antiferromagnetic transition close to 30 K. However, its nano counterpart has shown remarkable change in magnetic properties—a suppression of ferrimagnetic transition accompanied by strengthening low-temperature magnetic phase and observation of a new transition at 90 K ( T P ), which is weakly magnetic in nature. The frequency-dependent ac susceptibility data of nanoparticles have been fitted to the well-known de Almeida–Thouless equation and a H 2/3 dependence of the low-temperature peak is observed with a resulting zero-field freezing temperature ( T f 0 ) equal to 10.1 K. Further, the dynamical behaviour near freezing temperature has been analysed in terms of critical behaviour and the obtained fitted parameter values were found to be τ 0 (relaxation time constant) = 3.6 × 10 −6  s, T f 0  = 8.7 K and zν = 11.1. Moreover, Vogel–Fulcher law has been used to understand the nature of freezing transition, and the parameters after fitting are obtained as E a / k B  = 58.9 K, τ 0  = 5.22 × 10 −8  s and T 0  = 8.03 K. Finally, the spin-glass phase is concluded. Moreover, in contrast to bulk, the H 2/3 dependence of freezing temperature of nanoparticles sample (75 h) does support the 2D surface-like spin-glass nature.

Spin structures of nanoscale magnetic dots are the subject of increasing scientific effort, as the confinement of spins imposed by the geometrical restrictions makes these structures comparable to some internal characteristic length scales of the magnet. For a vortex (a ferromagnetic dot with a curling magnetic structure), a spot of perpendicular magnetization has been theoretically predicted to exist at the center of the vortex. Experimental evidence for this magnetization spot is provided by magnetic force microscopy imaging of circular dots of permalloy (Ni80Fe20) 0.3 to 1 micrometer in diameter and 50 nanometers thick.