Magnetic molecules as sensors of topological hysteresis of superconductors

Superconductors and magnetic materials, including molecules, are key ingredients for quantum and advanced spintronic applications. However, only a little is known about how these materials are mutually influenced at their interface in hybrid architectures. Here, we show that a single layer of magnetic molecules, the Terbium(III) bis-phthalocyaninato (TbPc2) complexes, deposited on a superconducting Pb(111) surface is sensitive to the topology of the intermediate state of the superconductor, namely to the presence and evolution of superconducting and normal domains due to the magnetic field screening and penetration. The evidence of this sensitivity is found in the magnetisation dynamics of the TbPc2 sub-monolayer in its paramagnetic regime showing the fingerprint of the topological hysteresis of the superconducting substrate. This study reveals the great potentialities hold by thin layers of magnetic molecules for sensing local magnetic field variation in hybrid molecular/superconductor architectures, including spin resonators or spin injection devices for spintronics applications.

Local Magnetic Field Promoted Photocatalytic Overall Water Splitting with Remarkable Solar-to-Hydrogen Efficiency

The photocatalytic overall water splitting (POWS) reaction using particulate catalysts is considered as an ideal approach for capturing solar energy and storing it in the form of hydrogen, however, current...

Geometry of Magnetic Fluctuations near the Sun from the Parker Solar Probe

Solar wind magnetic fluctuations exhibit anisotropy due to the presence of a mean magnetic field in the form of the Parker spiral. Close to the Sun, direct measurements were not available until the recently launched Parker Solar Probe (PSP) mission. The nature of the anisotropy and geometry of the magnetic fluctuations play a fundamental role in dissipation processes and in the transport of energetic particles in space. Using PSP data, we present measurements of the geometry and anisotropy of the inner heliosphere magnetic fluctuations, from fluid to kinetic scales. The results are surprising and different from 1 au observations. We find that fluctuations evolve characteristically with size scale. However, unlike 1 au solar wind, at the outer scale, the fluctuations are dominated by wavevectors quasi-parallel to the local magnetic field. In the inertial range, average wavevectors become less field aligned, but still remain more field aligned than near-Earth solar wind. In the dissipation range, the wavevectors become almost perpendicular to the local magnetic field in the dissipation range, to a much higher degree than those indicated by 1 au observations. We propose that this reduced degree of anisotropy in the outer scale and inertial range is due to the nature of large-scale forcing outside the solar corona.

Nanocavity-Mediated Fast Magnetic Vortex Core In-Situ Switching by Local Magnetic Field

Fast in situ switching of magnetic vortex core in a ferromagnetic nanodisk assisted by a nanocavity, with diameter comparable to the dimension of a vortex core, is systematically investigated by changing the strength as well as the diameter of the effective circular region of the applied magnetic field. By applying a local magnetic field within a small area at the nanodisk center, fast switching time of about 35 ps is achieved with relatively low field strength (70 mT) which is beneficial for fast data reading and writing. The reason for this phenomenon is that the magnetic spins around the nanocavity is aligned along the cavity wall due to the shape anisotropy when the perpendicular field is applied, which deepens the dip around the vortex core, and thus facilitates the vortex core switching.

Kinetic Plasma Turbulence Generated in a 3D Current Sheet With Magnetic Islands

In this article we aim to investigate the kinetic turbulence in a reconnecting current sheet (RCS) with X- and O-nullpoints and to explore its link to the features of accelerated particles. We carry out simulations of magnetic reconnection in a thin current sheet with 3D magnetic field topology affected by tearing instability until the formation of two large magnetic islands using particle-in-cell (PIC) approach. The model utilizes a strong guiding field that leads to the separation of the particles of opposite charges, the generation of a strong polarization electric field across the RCS, and suppression of kink instability in the “out-of-plane” direction. The accelerated particles of the same charge entering an RCS from the opposite edges are shown accelerated to different energies forming the “bump-in-tail” velocity distributions that, in turn, can generate plasma turbulence in different locations. The turbulence-generated waves produced by either electron or proton beams can be identified from the energy spectra of electromagnetic field fluctuations in the phase and frequency domains. From the phase space analysis we gather that the kinetic turbulence may be generated by accelerated particle beams, which are later found to evolve into a phase-space hole indicating the beam breakage. This happens at some distance from the particle entrance into an RCS, e.g. about 7di (ion inertial depth) for the electron beam and 12di for the proton beam. In a wavenumber space the spectral index of the power spectrum of the turbulent magnetic field near the ion inertial length is found to be −2.7 that is consistent with other estimations. The collective turbulence power spectra are consistent with the high-frequency fluctuations of perpendicular electric field, or upper hybrid waves, to occur in a vicinity of X-nullpoints, where the Langmuir (LW) can be generated by accelerated electrons with high growth rates, while further from X-nullponts or on the edges of magnetic islands, where electrons become ejected and start moving across the magnetic field lines, Bernstein waves can be generated. The frequency spectra of high- and low-frequency waves are explored in the kinetic turbulence in the parallel and perpendicular directions to the local magnetic field, showing noticeable lower hybrid turbulence occurring between the electron’s gyro- and plasma frequencies seen also in the wavelet spectra. Fluctuation of the perpendicular electric field component of turbulence can be consistent with the oblique whistler waves generated on the ambient density fluctuations by intense electron beams. This study brings attention to a key role of particle acceleration in generation kinetic turbulence inside current sheets.

Transient buildup and dissipation of a compressed plasma shockwave in arc-discharge plasma beams

Electric propulsion offers the advantage of a high specific impulse through a large exhaust velocity and has seen significant progress in space flight applications. Recently, we observed a transient plasma shockwave during pulsed plasma thruster operation when the plasma beam impacted a probe surface. However, details regarding the plasma shockwave formation are still unknown. This work is an experimental investigation of the compression-induced plasma shockwave in the presence of a planar obstruction. To study the complete shockwave buildup and dissipation process, an ultra-high-speed imaging system was set up to visualize the time-resolved shockwave morphology at a sub-microsecond level. In addition, the local magnetic field and plasma density were measured using 2-D magnetic coils and a triple Langmuir probe, respectively. The successive images of the shockwave give us a comprehensive understanding of the shockwave buildup process. During the 12 μs operational period of the thruster, two shockwaves were formed during the first cycle of the discharge. It is also interesting to note that there is a 1 μs dissipation period between the two shockwaves with the same cloud of plasma compressing against the probe surface. A shockwave model is also developed to predict the appearance of the two shockwaves. The implication is that the local magnetic field strength can be a key indicator for the plasma shockwave buildup and dissipation process.

Pemetaan batuan penyusun candi di bawah permukaan berdasarkan metode geomagnetik studi kasus: cagar budaya candi Songgiriti desa Songgokerto kecamatan Batu kota Batu

The geomagnetic method is often used in petroleum, geothermal and mineral exploration and can be applied to searching prospect archaeological objects (Siahaan, 2009). Several studies has been used the geomagnetic method to seek for archaeological objects by Ariani (2012) in Losari Temples and Sismanto et al (1997) in Kedulan Temple. In Batu City there is one of the cultural heritage that have not been intact called Songgoriti Temple. So, in this research we expected the existence of temple’s rocks using geomagnetic method. The de sign of the research using geomagnetic methods begins with the study of litera ture. This research was conducted with two methods there is calculating the val ue of the magnetic susceptibility of samples Temple’s rock using Bartington Susceptibility Meter MS2B and retrieving data field using the Proton magneto meter type ENVI SCINTREX. In the end of this research, we accepted the re sults of the two methods were compared to find out the site rock of temple. In magnetometer data analysis, data is processed using Magpick software, surfer 9.0 software and Mag2dc software. The results of the research show that a local magnetic field patterns of rocks in the area of cultural heritage Songgoriti Tem ple is divided into three parts namely high local magnetic field (yellow to red), the moderate local magnetic field (green to yellow) and low local magnetic field (blue). Furthermore based on five cross-sectional modeling using Mag2dc, we obtained the prediction the site of temple Songgoriti that is the sample number 1 found on the 2 position i.e at coordinates 49S 664547.5m 9130115m and coor dinate 49S 664585m 9130105m; sample number 3 found on the 2 position i.e at coordinates 49S 664583m 9130100m and coordinate 49S 664585m 9130100m; sample number 4 found on the 2 position i.e. at coordinates 49S 664577.5m 9130115m and coordinate 49S 664577.5m 9130110m; sample number 5 found on the 3 position i.e. at coordinates 49S 664566m 9130095m, coordinates 49S 664573m 9130095m and coordinate 49S 664582.5 m 9130095m; sample num ber 6 is found in 5 position i.e. at coordinates 49S 664545.5 m 9130110m, coordinates 49S 664550m 9130110m, coordinates 49S 664546m 9130105m, coordinates 49S 664565m 9130105m and coordinates 49S 664562.5 m 9130100m. For sample number 2 that is not found at all in the five models cross section. This may be caused by the value of the magnetic susceptibility sample number 2 is minor when compared to another samples that is 0.86 x 10-6 m3/kg

Quantum chemical insight into the effects of the local electron environment on T2*-based MRI

T2* relaxation is an intrinsic magnetic resonance imaging (MRI) parameter that is sensitive to local magnetic field inhomogeneities created by the deposition of endogenous paramagnetic material (e.g. iron). Recent studies suggest that T2* mapping is sensitive to iron oxidation state. In this study, we evaluate the spin state-dependence of T2* relaxation using T2* mapping. We experimentally tested this physical principle using a series of phantom experiments showing that T2* relaxation times are directly proportional to the spin magnetic moment of different transition metals along with their associated magnetic susceptibility. We previously showed that T2* relaxation time can detect the oxidation of Fe2+. In this paper, we demonstrate that T2* relaxation times are significantly longer for the diamagnetic, d10 metal Ga3+, compared to the paramagnetic, d5 metal Fe3+. We also show in a cell culture model that cells supplemented with Ga3+ (S = 0) have a significantly longer relaxation time compared to cells supplemented with Fe3+ (S = 5/2). These data support the hypothesis that dipole–dipole interactions between protons and electrons are driven by the strength of the electron spin magnetic moment in the surrounding environment giving rise to T2* relaxation.

Skyrmion Formation in Nanodisks Using Magnetic Force Microscopy Tip

We demonstrated numerically the skyrmion formation in ultrathin nanodisks using a magnetic force microscopy tip. We found that the local magnetic field generated by the magnetic tip significantly affects the magnetization state of the nanodisks and leads to the formation of skyrmions. Experimentally, we confirmed the influence of the local field on the magnetization states of the disks. Micromagnetic simulations explain the evolution of the magnetic state during magnetic force microscopy scanning and confirm the possibility of skyrmion formation. The formation of the horseshoe magnetic domain is a key transition from random labyrinth domain states into the skyrmion state. We showed that the formation of skyrmions by the magnetic probe is a reliable and repetitive procedure. Our findings provide a simple solution for skyrmion formation in nanodisks.