Spin-based electronics has evolved into a major field of research that broadly encompasses different classes of materials, magnetic systems, and devices. This review describes recent advances in spintronics that have the potential to impact key areas of information technology and microelectronics. We identify four main axes of research: nonvolatile memories, magnetic sensors, microwave devices, and beyond-CMOS logic. We discuss state-of-the-art developments in these areas as well as opportunities and challenges that will have to be met, both at the device and system level, in order to integrate novel spintronic functionalities and materials in mainstream microelectronic platforms.Conventional information processing and communication devices work by controlling the flow of electric charges in integrated circuits. Such circuits are based on nonmagnetic semiconductors, in Technologies based on GMR and MTJ devices are now firmly established and compatible with CMOS fab processes. Yet, in order to meet the increasing demand for high-speed, high-density, and low power electronic components, the design of materials, processes, and spintronic circuits needs to be continuously innovated. Further, recent breakthroughs in basic research brought forward novel phenomena that allow for the generation and interconversion of charge, spin, heat, and optical signals.Many of these phenomena are based on non-equilibrium spin-orbit interaction effects, such as the spin Hall and Rashba-Edelstein effects 6,8,23 or their thermal 24 and optical 25,26 analogues. Spin-orbit torques (SOT), for example, can excite any type of magnetic materials, ranging from metals to semiconductors and insulators, in both ferromagnetic and antiferromagnetic configurations 6 . This versatility allows for the switching of single layer ferromagnets, ferrimagnets, and antiferromagnets, as well as for the excitation of spin waves and auto-oscillations in both planar and vertical device geometries 10,11 . Charge-spin conversion effects open novel pathways for information processing using Boolean logic, as well as promising avenues for implementing unconventional neuromorphic 27,28,29 and probabilistic 30 computing schemes. Finally, spintronic devices cover a broad bandwidth ranging from DC to THz 31,32 , leading to exciting opportunities for the on-chip generation and detection of high frequency signals.

NiO/Ni wires have been investigated as a function of their width in order to investigate the size dependence of exchange bias. The samples have been prepared by e-beam lithography and ion milling of ion beam sputtered thin films. For NiO/Ni wires narrower than 3 m, the exchange bias field significantly depends on the wire width. A NiO/Ni film shows an exchange bias field of Ϫ78 Oe whereas the exchange bias field of wires narrower than 200 nm is reduced to approximately Ϫ40 Oe. The coercive field of the NiO/Ni film is 28 Oe and increases to 210 Oe for the narrowest wires. The decrease of the exchange bias field for the narrowest wires is consistent with a recent microscopic model of exchange bias where the appearance of a unidirectional anisotropy in ferromagnet/antiferromagnet bilayers has been attributed to the presence of antiferromagnetic domains in the bulk of the antiferromagnet. A possible onset of a transition from a multidomain to a single-domain state of the antiferromagnet as a function of the NiO/Ni wire width seems to be the origin for the observed decrease of the exchange bias field for narrow wires.The exchange bias ͑EB͒ effect occurs due to the exchange coupling at antiferromagnet͑AFM͒/ferromagnet͑FM͒ interfaces leading to a shift of the magnetic hysteresis loop along the field axis.1 This shift of the hysteresis loop can be established either by cooling the AFM/FM bilayers in a magnetic saturation field below the Néel temperature T N of the AFM or by depositing the bilayers in an external magnetic field.2 The exchange bias effect has been used over several decades and more recently for pinning the magnetization of one of the two electrodes in magnetoresistive devices ͑giant magnetoresistance multilayers 3 and tunnel junctions 4,5͒. Although the exchange bias effect has already been intensively exploited in micron-and submicron-sized magnetoelectronic devices, its microscopic origin is not yet fully understood.A recent experiment on Co/CoO bilayers in conjunction with a Monte Carlo simulation study has shown that the dilution of the antiferromagnet CoO with nonmagnetic impurities ͑e.g., Co 1Ϫx Mg x O͒ or defects ͑e.g., Co 1Ϫy O͒ in its volume part leads to the formation of antiferromagnetic volume domains. 6 The formation of antiferromagnetic domain walls leads to a small surplus magnetization at the AFM/FM interface which couples to the FM and results in a unidirectional anisotropy. Hence, the antiferromagnetic domains are the microscopic origin of exchange bias. This result is complementary to a previous approach attributing exchange bias to the formation of antiferromagnetic domains with domain walls ͑DW͒ perpendicular to the AFM/FM interface in the presence of only interface roughness.7 From these models one has to conclude that the exchange bias of AFM/FM bilayers vanishes when the AFM becomes single domain. From a systematic investigation of a possible finite size effect of exchange bias the microscopic role of the DW formation can be elucidated as well as the lower limit of the extension of...

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Topographical cues of magnetically responsive tendon mimetic 3D scaffolds in combination with magneto-mechanical stimulation of human adipose stem cells synergistically boost their tenogenesis.

In agreement with recent model calculations on interacting magnetic nanoparticles the magnetic relaxation of a field-cooled superferromagnetic ͑SFM͒ granular multilayer ͓Co 80 Fe 20 (1.4 nm)/Al 2 O 3 (3 nm)͔ 10 follows a power-law decay retaining a finite asymptotic remanence. Unexpectedly, a second isothermal upward relaxation is observed after field quenching the sample. It is attributed to slow equilibration of the thermoremanent magnetization inside the SFM domains. Magnetization hole burning via aging reveals the chaotic nature of the domain state.Magnetic single-domain nanoparticles ͑''superspins''͒ and their mutual interactions are very interesting not only for potential applications but also for rich fundamental research in magnetism. It is well known that highly diluted magnetic nanoparticle systems show superparamagnetic ͑SPM͒ behavior as described by the Néel-Brown model 1 for isolated particles when the magnetic dipole interactions between particles are negligible. When interparticle interactions are involved, the system eventually shows collective behavior which overcomes the individual anisotropy properties of the particles. Superspin glass ͑SSG͒ was found at low-enough temperatures for intermediate particle densities. 2 Apart from classical dipole interaction, 3-5 exchange and other nonclassical interactions 6,7 were considered at higher particle densities. Superferromagnetic ͑SFM͒ ordering due to tunneling exchange was claimed to occur in quasi-one-dimensional Fe particle arrays 8 and probably also occurs in Co/Cu͑100͒ ultrathin films just below the percolation threshold of the Co islands. 9 However, SFM ordering may even occur in purely dipolar systems, e.g., in regular two-dimensional superspin lattices. 4,5 Recently, the concentration dependent crossover between SSG and SFM behavior has been evidenced in discontinuous magnetic metal-insulator multilayers ͑DMIM͒ ͓Co 80 Fe 20 (t n )/Al 2 O 3 (3 nm)͔ 10 . 10 These granular systems were found to possess generic spin-glass behavior for nominal CoFe thicknesses t n р1 nm, 11 while SFM behavior with domain state properties is encountered at t n у1.2 nm, 12 but below the percolation limit, t n ϭ1.8 nm, above which Ohmic conduction and ordinary ferromagnetism are encountered. 13 Three elements of randomness are involved: a finite dispersion of the superspin sizes ͓e.g. magnetic moments m Ϸ(3.0Ϯ0.3)ϫ10 3 B for t n ϭ0.9 nm, where B is Bohr's magneton 14 ͔, random anisotropy axes around a preferential in-plane direction as defined by an external magnetic field BϷ3 mT applied during the multilayer growth, 15 and a random spatial distribution with tendency towards hexagonal self-assembly within the planes and smecticlike periodicity along the film normal. 14 A similar scenario was recently chosen in Monte Carlo simulations on an ensemble of superspins with random spatial distribution, anisotropy, and spin sizes by Ulrich et al. 16 They observed a crossover between different asymptotic de-cay laws ranging from stretched exponential behavior, m TRM (t)ϭm 0 exp...

Liquid biopsy offers unique opportunities for low invasive diagnosis, real-time patient monitoring and treatment selection. The phenotypic and molecular profile of circulating tumor cells (CTCs) can provide key information about the biology of tumor cells, contributing to personalized therapy. CTC isolation is still challenging, mainly due to their heterogeneity and rarity. To overcome this limitation, a microfluidic chip for label-free isolation of CTCs from peripheral blood was developed. This device, the CROSS chip, captures CTCs based on their size and deformability with an efficiency of 70%. Using 2 chips, 7.5 ml of whole blood are processed in 47 minutes with high purity, as compared to similar technologies and assessed by in situ immunofluorescence. The CROSS chip performance was compared to the CellSearch system in a set of metastatic colorectal cancer patients, resulting in higher capture of DAPI+/CK+/CD45− CTCs in all individuals tested. Importantly, CTC enumeration by CROSS chip enabled stratification of patients with different prognosis. Lastly, cells isolated in the CROSS chip were lysed and further subjected to molecular characterization by droplet digital PCR, which revealed a mutation in the APC gene for most patient samples analyzed, confirming their colorectal origin and the versatility of the technology for downstream applications.

Bovine mastitis is an inflammation of the mammary gland caused by a multitude of pathogens with devastating consequences for the dairy industry. Global annual losses are estimated to be around €30 bn and are caused by significant milk losses, poor milk quality, culling of chronically infected animals, and occasional deaths. Moreover, mastitis management routinely implies the administration of antibiotics to treat and prevent the disease which poses serious risks regarding the emergence of antibiotic resistance. Conventional diagnostic methods based on somatic cell counts (SCC) and plate-culture techniques are accurate in identifying the disease, the respective infectious agents and antibiotic resistant phenotypes. However, pressure exists to develop less lengthy approaches, capable of providing on-site information concerning the infection, and in this way, guide, and hasten the most adequate treatment. Biosensors are analytical tools that convert the presence of biological compounds into an electric signal. Benefitting from high signal-to-noise ratios and fast response times, when properly tuned, they can detect the presence of specific cells and cell markers with high sensitivity. In combination with microfluidics, they provide the means for development of automated and portable diagnostic devices. Still, while biosensors are growing at a fast pace in human diagnostics, applications for the veterinary market, and specifically, for the diagnosis of mastitis remain limited. This review highlights current approaches for mastitis diagnosis and describes the latest outcomes in biosensors and lab-on-chip devices with the potential to become real alternatives to standard practices. Focus is given to those technologies that, in a near future, will enable for an on-farm diagnosis of mastitis.