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Made of a thin non-superconducting metal (N) sandwiched by two superconductors (S), SNS Josephson junctions enable novel quantum functionalities by mixing up the intrinsic electronic properties of N with the superconducting correlations induced from S by proximity. Electronic properties of these devices are governed by Andreev quasiparticles [1] which are absent in conventional SIS junctions whose insulating barrier (I) between the two S electrodes owns no electronic states. Here we focus on the Josephson vortex (JV) motion inside Nb-Cu-Nb proximity junctions subject to electric currents and magnetic fields. The results of local (Magnetic Force Microscopy) and global (transport) experiments provided simultaneously are compared with our numerical model, revealing the existence of several distinct dynamic regimes of the JV motion. One of them, identified as a fast hysteretic entry/escape below the critical value of Josephson current, is analyzed and suggested for low-dissipative logic and memory elements., Comment: 11 pages, 3 figures, 1 table, 43 references

Novel, structurally stable hybrid magnetic materials based on polymers of natural origin and containing superparamagnetic iron oxide nanoparticles (SPIONs) were obtained. SPIONs coated with the chitosan derivative were linked with the chitosan-collagen hydrogel matrix by the covalent bonds formed between the macromolecules of nanoparticles' coating and matrix on their crosslinking with genipin. The systems obtained were structurally stable as confirmed by turbidity studies. Their microstructure was determined by electron microscopy studies (SEM). The homogenic distribution of SPIONs in hybrid materials was observed by Scanning Transmission Electron Microscopy (STEM). Magnetic force microscopy (MFM) confirmed the magnetic properties of hybrids and SPIONs distribution within the samples. The rheological studies allowed to determine the effect of hybrid material composition on their mechanical properties (storage modulus). Magnetic characterization confirmed that SPIONs preserved their superparamagnetic properties in the hybrid materials fabricated.

Magnetic resonance force microscopy is becoming increasingly important for three-dimensional image reconstruction inside a sample with non-invasive measurements. In this study, a magnetic resonance force sensor with a vacuum-packaged magnetic cantilever was developed for the detection of free radicals in an atmospheric environment. A 1.5- $\mu \text{m}$ -thick silicon-based cantilever, which was mounted with a 25- $\mu \text{m}$ -diameter Nd-Fe-B magnet at the end of the cantilever, was hermetically packaged in a vacuum cavity using an anodic-bonding technique. The evaluation of the pressure dependence on the quality factor of the mechanical magnet-based cantilever revealed that the packaged-cavity pressure was approximately in the range of $7.3\,\,\times10$ 2– $1.0\,\,\times10$ 3 Pa after vacuum packaging. The corresponding detection sensitivity of the magnet-based cantilever sensor was calculated to be $1.1\,\,\times10$ -13 N/ $\sqrt {Hz} $ . Based on the magnetic force interaction, the magnetic field gradients were detected by mapping the variations in the resonant frequency and resonant amplitude of the magnetic cantilever. Finally, the magnetic resonance force, caused by the electron spin resonance in a standard radical of 1, 1-Diphenyl-2-picrylhydrazyl, was detected with a spin density of $\sim 1.5\,\,\times10$ 15 spins/cm3 in an atmospheric environment. The proposed vacuum-packaged magnet-based cantilever confirmed the high feasibility of magnetic resonance force detection within a non-hermetic environment.

Nanoscale magnetic imaging can provide microscopic information about length scales, inhomogeneity and interactions of materials systems. As such, it is a powerful tool to probe phenomena such as superconductivity, Mott insulating states and magnetically ordered states in 2D materials, which are sensitive to the local environment. This Technical Review provides an analysis of weak magnetic field imaging techniques that are most promising for the study of 2D materials: magnetic force microscopy, scanning superconducting quantum interference device microscopy and scanning nitrogen-vacancy centre microscopy., Nature Reviews Physics, 4 (1), ISSN:2522-5820

In this study, we proposed a new method to prepare yttrium iron garnet/yttrium iron garnet (YIG/YIG) functional joint via in-situ synthesis of novel Co2FeO4 needle-like phases. It is found that the formation of the Co2FeO4 needle-like phases was controlled by “two-step heterogeneous nucleation”: (i) CoO nanoparticles acted as the preliminary heterogeneous nucleation particle, reacting with O2 to form Co3O4 phase; (ii) The surface of Co3O4 phase acted as the subsequent heterogeneous nucleation interface, atoms stacked along the (220) crystal plane of Co3O4 to form Co2FeO4 phase. Fe3+ diffused into the glass matrix which is rich in O2−, participating in the reaction with Co3O4 and CoO. The Co2FeO4 nuclei grew into needle-like phases along the [001] orientation. The Co2FeO4 needle-like phases exhibited favourable mechanical property and magnetism according to the nanoindentation and magnetic force microscopy (MFM) analysis. And the shear strength of YIG/YIG joint reinforced by Co2FeO4 needle-like phases could reach 72 MPa. The investigation supplies a new synthetic idea of Co2FeO4 magnetic needle-like phases, which has significant application potential for the structural and functional integration in electromagnetic field.

—CoPt films obtained by electron beam evaporation with deposition of ten Co and Pt bilayers with a total thickness of 8 nm are experimentally investigated. The Hall effect and longitudinal magnetoresistance measurements were carried out with a temperature change from 8 to 300 K. At room temperature, using magnetic force microscopy, images of domain structures corresponding to different points of the magnetization reversal curve were obtained. The possibility of studying the Hall effect on artificially created domain structures formed by the local magnetic field of the probe of an atomic force microscope is demonstrated.

The CE phase is an extraordinary phase exhibiting the simultaneous spin, charge, and orbital ordering due to strong electron correlation. It is an ideal platform to investigate the role of the multiple orderings in the phase transitions and discover emergent properties. Here, we use a cryogenic high-field magnetic force microscope to image the phase transitions and properties of the CE phase in a Pr0.5Ca0.5MnO3 thin film. In a high magnetic field, we observed a clear suppression of magnetic susceptibility at the charge-ordering insulator transition temperature (TCOI), whereas, at the Néel temperature (TN), no significant change is observed. This observation favors the scenario of strong antiferromagnetic correlation developed below TCOI but raises questions about the Zener polaron paramagnetic phase picture. Besides, we discoverd a phase-separated surface state in the CE phase regime. Ferromagnetic phase domains residing at the surface already exist in zero magnetic field and show ultra-high magnetic anisotropy. Our results provide microscopic insights into the unconventional spin- and charge-ordering transitions and revealed essential attributes of the CE phase, highlighting unusual behaviors when multiple electronic orderings are involved.

Noncollinear spin textures have attracted much attention due to their novel physical behaviors in heavy/ferromagnetic metal (HM/FM) systems. The transport anomaly, appearing as contrast humps in Hall resistivity curves, is the mark of noncollinear spin textures. Here, the epitaxial Pt/γ'-Fe4N bilayers with noncollinear spin textures were obtained by facing target sputtering. Large micromagnetic Dzyaloshinskii-Moriya interaction coefficient D of 2.90 mJ/m2 appears in Pt/γ'-Fe4N/MgO systems, which is larger than 2.05 mJ/m2 of Pt/Co/MgO systems with skyrmionic states. Moreover, at 300 K, magnetic bubble-like domains appear in Pt/γ'-Fe4N bilayers that just possess a 3 nm thick ferromagnetic layer instead of [HM/FM]n or [HM1/FM/HM2]n multilayers. Additionally, a room-temperature transport anomaly appears in Pt/γ'-Fe4N/MgO systems. The contrast humps of Pt(3 nm)/γ'-Fe4N(tFe4N ≤ 4 nm)/MgO heterostructures are not sharp due to the nonuniform distributions of the magnetic bubble-like domains with various sizes and irregular shapes, as observed by the magnetic force microscopy. The discovery of epitaxial Pt/γ'-Fe4N bilayers with noncollinear spin states is more crucial than that of polycrystalline or amorphous HM/FM systems for reducing ohmic heating, which provides a candidate for noncollinear spintronic applications.

The influence of temperature on the magnetization distribution of planar Co18Ni82 microparticles deposited on a lithium niobate single crystal was studied using the magnetic force microscopy and co...

This study considers an inverse problem, where the corresponding forward problem is given by a finite-dimensional linear operator T. The inverse problem has the following form: (data)=T(unknown). I...

In this study, a preparation route of Co-Cu alloys with soft magnetic properties by high-pressure torsion deformation is introduced. Nanocrystalline, supersaturated single-phase microstructures are obtained after deformation of Co-Cu alloys, which are prepared from an initial powder mixture with Co-contents above 70 wt.%. Isochronal annealing treatments up to 400{\deg}C further reveal a remarkable microstructural stability. Only at 600{\deg}C, the supersaturated phase decomposes into two fcc-phases. The coercivity, measured by SQUID as a function of annealing temperature, remains significantly below the value for bulk-Co in all states investigated. In order to understand the measured magnetic properties in detail, a quantitative analysis of the magnetic microstructure is carried out by magnetic force microscopy and correlated to the observed changes in coercivity. Our results show that the rising coercivity can be explained by a magnetic hardening effect occurring in context with spinodal decomposition.

We report the pure voltage manipulation of desired in-plane magnetization orientation of the nanomagnets in Ni/PMN-PT multiferroic heterostructure and systemically studies the effect of localized stress on the magnetization orientation by magnetic force microscope. Referable analysis about the dynamic magnetization process of the nanomagnet are provided by micromagnetic simulation. Both the experiments and simulations have proved that the 180 degrees switching of the nanomagnets can be induced without strict requirements of the voltage waveform. The results can be effectively applied to electrical induced logic writing of low-energy-consumption spintronic devices.

The possibility of using implantation of 20-keV He+ ions for modification of the domain structure and magnetic properties of CoPt films (formed by the electron-beam evaporation method) with different cobalt contents (Co0.45Pt0.55 and Co0.35Pt0.65) has been investigated. A decrease in the coercive field (narrowing of the hysteresis loop in the magnetic-field dependences of the Faraday angle and magnetization) with an increase in the He+ ion fluence from 2 × 1014 to 4 × 1014 cm–2 has been found for the irradiated CoPt samples of both compositions. The residual magnetization of the Co0.35Pt0.65 films coincides with the saturation magnetization, and a decrease in the residual magnetization is observed for Co0.45Pt0.55. It is shown by magnetic force microscopy that the largest number of round isolated domains (skyrmions) for the Co0.45Pt0.55 alloy are formed when the ion fluence increases to 3 × 1014 cm–2, while 360-degree domain walls (1D skyrmions) are observed along with round isolated domains for the Co0.35Pt0.65 films irradiated with a He+ fluence of 4 × 1014 cm–2. An analysis of CoPt films by Mandelstam–Brillouin spectroscopy revealed an increase in the shift between the Stokes and anti-Stokes components of the spectrum and a significant enhancement of the Dzyaloshinski–Moriya interaction in the irradiated samples. Model calculations performed using the SRIM program showed that the ion irradiation facilitates asymmetric mixing of Co and Pt atoms in CoPt films, which may underlie the mechanism of the observed effects of ion irradiation on their magnetic properties and domain structure.

A previous work has shown that a modified HP-NbTi heat-resistant stainless steel exhibited a different magnetic behavior after 90,000 hours of operation in a steam reformer furnace exposed to temperatures between 500 °C and 550 °C or between 950 °C and 1000 °C. In this work, in the sample exposed to the lower temperature range, a thin ferromagnetic layer was detected by magnetic force microscopy in the matrix around the chromium and niobium carbides. However, for the sample exposed to the higher temperature range, no ferromagnetic response was detected whatsoever. The understanding of the influence of microstructure on magnetic behavior is important for the development of non-destructive inspection test methodologies. For this reason, the aim of this study is to perform a microstructural analysis to assess the different magnetic responses. Transmission electron microscopy allowed identifying a Cr-depleted zone in austenite at the Cr23C6-matrix and (NbTi)C-matrix interfaces in the sample exposed to the lower temperature range. Therefore, the austenitic region, with a lower Cr content, becomes ferromagnetic. In the sample exposed to the higher temperature range, the chemical composition of the austenitic matrix was homogenous, and the sample was completely paramagnetic.

Mechanical control is essential for adaptive regulation in biological systems. This work presents a magnetic, non-contact approach to simultaneous detection and actuation in a microscale tissue testbed. The platform builds upon previously developed passive mechanical platforms, where tissues self-assemble on flexible pillars. Standard detection is typically derived from microscope images and actuation is often conducted using invasive approaches. In the presented platform, actuation and detection, both derived from magnetic fields, are demonstrated with high spatial, temporal, and force resolution resulting in a detectable $0.6~\mu \text{m}$ step-size in air. The forced deflection range is +/−125 microns (+/−10% strain), and an arbitrary magnitude step-and-settle actuation is achieved in less than 1 ms. Engineered human cardiac microtissue is used to demonstrate the capabilities of the system, as cardiac tissues generate contractions and adapt to external forces. Spontaneous contractions are monitored for an hour by a built-in sensor with a signal-to-noise of 2. Cyclic actuation at 1 Hz using a 1 mT/mm magnetic field is demonstrated, where max tissue strain is 0.3%. All this is achieved in a moderate-throughput, compact device, which is easily integrated into the typical flow of biological experimentation. Simultaneous control of actuation and detection enables decisions to be made on a sample-specific basis, and in future developments, will enable arbitrary design of the mechanical environment for 3D tissue conditioning, maturation, and control. [2020-0296]