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Spintronic devices based on antiferromagnetic (AFM) materials hold the promise of fast switching speeds and robustness against magnetic fields1–3. Different device concepts have been predicted4,5 and experimentally demonstrated, such as low-temperature AFM tunnel junctions that operate as spin-valves6, or room-temperature AFM memory, for which either thermal heating in combination with magnetic fields7 or Néel spin–orbit torque8 is used for the information writing process. On the other hand, piezoelectric materials were employed to control magnetism by electric fields in multiferroic heterostructures9–12, which suppresses Joule heating caused by switching currents and may enable low-energy-consuming electronic devices. Here, we combine the two material classes to explore changes in the resistance of the high-Néel-temperature antiferromagnet MnPt induced by piezoelectric strain. We find two non-volatile resistance states at room temperature and zero electric field that are stable in magnetic fields up to 60 T. Furthermore, the strain-induced resistance switching process is insensitive to magnetic fields. Integration in a tunnel junction can further amplify the electroresistance. The tunnelling anisotropic magnetoresistance reaches ~11.2% at room temperature. Overall, we demonstrate a piezoelectric, strain-controlled AFM memory that is fully operational in strong magnetic fields and has the potential for low-energy and high-density memory applications.

The discovery of magnetic order in atomically-thin van der Waals materials has strengthened the alliance between spintronics and two-dimensional materials. An important use of magnetic two-dimensional materials in spintronic devices, which has not yet been demonstrated, would be for coherent spin injection via the spin-pumping effect. Here, we report spin pumping from Cr 2 Ge 2 Te 6 into Pt or W and detection of the spin current by inverse spin Hall effect. The magnetization dynamics of the hybrid Cr 2 Ge 2 Te 6 /Pt system are measured, and a magnetic damping constant of ~ 4–10 × 10 −4 is obtained for thick Cr 2 Ge 2 Te 6 flakes, a record low for ferromagnetic van der Waals materials. Moreover, a high interface spin transmission efficiency (a spin mixing conductance of 2.4 × 10 19 /m 2 ) is directly extracted, which is instrumental in delivering spin-related quantities such as spin angular momentum and spin-orbit torque across an interface of the van der Waals system. The low magnetic damping that promotes efficient spin current generation together with high interfacial spin transmission efficiency suggests promising applications for integrating Cr 2 Ge 2 Te 6 into low-temperature two-dimensional spintronic devices as the source of coherent spin or magnon current. Spin-pumping experimental technique where a DC or AC spin current is generated, and typically transferred to a heavy metal layer where it can be detected via electrical measurements. While well established in conventional materials, coherent spin-pumping in van der Waals magnetic materials is challenging due to the low damping and high-quality interface requirements. Here, Xu et al demonstrate coherent spin pumping in the van der Waals magnet Cr2Ge2Te6.

It is possible to suppress convection and dispersion of a paramagnetic liquid by means of a magnetic field. A tube of paramagnetic liquid can be stabilized in water along a ferromagnetic track in a vertical magnetic field, but not in a horizontal field. Conversely, an \"antitube\" of water can be stabilized in a paramagnetic liquid along the same track in a transverse horizontal field, but not in a vertical field. The stability arises from the interaction of the induced moment in the solution with the magnetic field gradient in the vicinity of the track. The magnetic force causes the tube of paramagnetic liquid to behave as if it were encased by an elastic membrane whose cross-section is modified by gravitational forces and Maxwell stress. Convection from the tube to its surroundings is inhibited, but not diffusion. Liquid motion within the paramagnetic tube, however, exhibits vorticity in tubes of diameter 1 mm or less--conditions where classical pipe flow would be perfectly streamline, and mixing extremely slow. The liquid tube is found to slide along the track almost without friction. Paramagnetic liquid tubes and antitubes offer appealing new prospects for mass transport, microfluidics, and electrodeposition.

When miniaturizing fluidic circuitry, the solid walls of the fluid channels become increasingly important 1 because they limit the flow rates achievable for a given pressure drop, and they are prone to fouling 2 . Approaches for reducing the wall interactions include hydrophobic coatings 3 , liquid-infused porous surfaces 4 – 6 , nanoparticle surfactant jamming 7 , changes to surface electronic structure 8 , electrowetting 9 , 10 , surface tension pinning 11 , 12 and use of atomically flat channels 13 . A better solution may be to avoid the solid walls altogether. Droplet microfluidics and sheath flow achieve this but require continuous flow of the central liquid and the surrounding liquid 1 , 14 . Here we demonstrate an approach in which aqueous liquid channels are surrounded by an immiscible magnetic liquid, both of which are stabilized by a quadrupolar magnetic field. This creates self-healing, non-clogging, anti-fouling and near-frictionless liquid-in-liquid fluidic channels. Manipulation of the field provides flow control, such as valving, splitting, merging and pumping. The latter is achieved by moving permanent magnets that have no physical contact with the liquid channel. We show that this magnetostaltic pumping method can be used to transport whole human blood with very little damage due to shear forces. Haemolysis (rupture of blood cells) is reduced by an order of magnitude compared with traditional peristaltic pumping, in which blood is mechanically squeezed through a plastic tube. Our liquid-in-liquid approach provides new ways to transport delicate liquids, particularly when scaling channels down to the micrometre scale, with no need for high pressures, and could also be used for microfluidic circuitry. Wall-free liquid channels surrounded by an immiscible magnetic liquid can be used to create liquid circuitry or to transport human blood without damaging the blood cells by moving permanent magnets.

The magnetic response of nanoparticles made from wide-bandgap oxides that don’t contain any magnetic cations is somewhat of a mystery. Experiments with CeO 2 suggest that the origin may be due to vacuum fluctuations. The magnetism of nanoparticles and thin films of wide-bandgap oxides that include no magnetic cations is an unsolved puzzle 1 . Progress has been hampered by both the irreproducibility of much of the experimental data, and the lack of any generally accepted theoretical explanation. The characteristic signature is a virtually anhysteretic, temperature-independent magnetization curve that saturates in an applied field that is several orders of magnitude greater than the magnetization. It would seem as if a tiny volume fraction, ≲0.1%, of the samples is magnetic and that the energy scale is unusually high for spin magnetism. Here we investigate the effect of dispersing 4 nm CeO 2 nanoparticles with powders of γAl 2 O 3 , sugar or latex microspheres. The saturation magnetization, M s ≍ 60 A m −1 for compact samples, is maximized by 1 wt% lanthanum doping. Dispersing the CeO 2 nanopowder reduces its magnetic moment by up to an order of magnitude, and there is a characteristic length scale of order 100 nm for the magnetism to appear in CeO 2 nanoparticle clusters. The phenomenon is explained in terms of a giant orbital paramagnetism that appears in coherent mesoscopic domains due to resonant interaction with zero-point fluctuations of the vacuum electromagnetic field. The theory explains the observed temperature-independent magnetization curve and its doping and dispersion dependence, based on a length scale of 300 nm that corresponds to the wavelength of a maximum in the ultraviolet absorption spectrum of the magnetic CeO 2 nanoparticles. The coherent domains occupy roughly 10% of the sample volume.

Although it is tempting to compare organic semiconductors with their inorganic counterparts, the spin-injection and spin-transport properties are fundamentally different. The challenges in understanding and improving such properties make organic spintronics an exciting field in its own right.

An electrochemical sensor was developed and tested for detection of L-tyrosine in the presence of epinephrine by surface modification of a glassy carbon electrode (GCE) with Nafion and cerium dioxide nanoparticles. Fabrication parameters of a surfactant-assisted precipitation method were optimized to produce 2–3 nm CeO 2 nanoparticles with very high surface-to-volume ratio. The resulting nanocrystals were characterized structurally and morphologically by X-ray diffractometery (XRD), scanning and high resolution transmission electron microscopy (SEM and HR-TEM). The nanopowder is sonochemically dispersed in a Nafion solution which is then used to modify the surface of a GCE electrode. The electrochemical activity of L-tyrosine and epinephrine was investigated using both a Nafion-CeO 2 coated and a bare GCE. The modified electrode exhibits a significant electrochemical oxidation effect of L-tyrosine in a 0.2 M Britton-Robinson (B-R) buffer solution of pH 2. The electro-oxidation peak current increases linearly with the L-tyrosine concentration in the molar concentration range of 2 to 160 μM. By employing differential pulse voltammetry (DPV) for simultaneous measurements, we detected two reproducible peaks for L-tyrosine and epinephrine in the same solution with a peak separation of about 443 mV. The detection limit of the sensor (signal to noise ratio of 3) for L-tyrosine is ~90 nM and the sensitivity is 0.20 μA μM −1 , while for epinephrine these values are ~60 nM and 0.19 μA μM −1 . The sensor exhibited excellent selectivity, sensitivity, reproducibility and stability as well as a very good recovery time in real human blood serum samples. Simultaneous electrochemical determination of L-tyrosine and epinephrine in blood plasma with Nafion-CeO 2 /GCE modified electrode showing a 443 mV peak-to-peak potential difference between species oxidation peak currents.

Transition metals form mixed-valence oxides that are expected to have ordered arrangements of d-shell electrons. But the ionic picture must be rethought to include oxygen \"holes\" in the charge-ordered patterns.