The application of low-field time-domain nuclear magnetic resonance (TD-NMR) to measure water content and assess moisture-related relaxation behavior in sludge samples has been investigated. The results of TD-NMR measurements on 26 dewatered sludge samples revealed a strong correlation between sludge water content and key features of the T2 distribution curves, including the maximum relaxation time and peak area, demonstrating the potential of the TD-NMR method for estimating sludge moisture content. No consistent relationship was observed between the peaks in T2 relaxation distribution curves obtained by Inverse Laplace Transform (ILT) and the expected water fraction ratios, apparently because the sludge structure is highly variable from sample to sample. Despite the complex and heterogeneous nature of sludge samples, the direct correspondence between key features of the T2 relaxation curves and moisture content demonstrates the high potential of TD-NMR as a tool for rapid and reliable moisture monitoring, even in an online device configuration.

Microwave-to-optical quantum transduction is a critically important task in the field of quantum information and communication technologies. Hybrid Quantum Systems (HQS), consisting of different interacting subsystems, are believed to be a physical base for the realization of quantum frequency conversion. HQSs based on magnetically ordered materials look like a very prospective solution due to the strong coupling between MW photons and magnetic oscillations. Another approach is based on rare-earth (RE) ions doped in crystals, which potentially provides an efficient way for magneto-optical quantum coherence transfer. In this work, we review approaches for quantum transduction based on both classes of materials (magnon- and RE-based). We analyze their specific features and compare the strong and weak sides of each material class. The possibility interfacing or combining these two approaches in a single device is also considered as well as the technical challenges of the practical realization of such a hybrid system.

The TD NMR technique was used to quantify the water content in three sludge samples, collected from a central wastewater treatment plant. The moisture content of sludge samples ($81.6 \%, 80.3 \%$, and 78 %) was established by thermal drying procedure. The Carr-Purcell-Meiboom-Gill (CPMG) pulse sequence was applied to obtain spin-spin relaxation curves. Various software packages for Inverse Laplace Transform (ILT) were applied to assess the $\mathrm{T}_{2}$ relaxation time distribution of the samples. We tested the influence of a Signal-To-Noise Ratio (SNR) on the results we received. We also established that the NNLS routine of PROSPA software, with the possibility to tune regularization parameters, provides the most stable and repeatable $T_{2}$ distribution curves.

Modeling of low-field NMR spectra with indirect spin-spin interaction (J-coupling) is not included in popular NMR software. Modeling NMR spectra for cases of various magnetic fields is necessary not only for the interpretation of spectra, but also for the planning of experiments. The developed versions of the program make it possible to obtain model NMR spectra with J-coupling at any values of the magnetic field. As examples, the real proton NMR spectra of triethyl phosphate at different magnetic fields are considered in comparison with model ones. The peculiarities of NMR spectra at certain values of magnetic field are discussed.

The optical properties of erbium-doped yttrium iron garnet (Er:YIG) thin films have been studied at temperatures between 1.6 K and 260 K. Single crystal YIG thin films on GGG (Gd3Ga5O12) have been implanted with 20 keV Er+ ions to the fluences of (0.5 or 1.0) x 10(16) ion/cm(2). Erbium concentration has been kept on a level preventing a detrimental effect on the magnetic properties of the YIG garnet while providing the ion ratio enough for intense photoluminescence. Raman spectra for the YIG films on GGG substrate which are similar to the literature data have been observed. No effect of the erbium implantation on Raman peaks has been revealed and explained by the small thickness of the implanted layer. Photoluminescence signals appearing with temperature cooling between 680 nm and 720 nm have been observed and attributed to the emission from the erbium ions. Our result reveals that doping YIG by Er can be useful for tailoring the magneto-optical properties of YIG.

High-resolution H-1 NMR, high-field H-1 NMR relaxometry, and low-field (<0.5 T) NMR relaxometry have been applied to study different types of olive and soybean oils. It has been shown that the use of spectral and relaxation information in high-field NMR is an effective tool for the detection of oil adulteration and identification of food oils, including oils with close content. We have also shown that low-field NMR relaxation measurements can be applied for the discrimination between various food oils in the case of a limited group of samples. This work has demonstrated the possibilities of the different types of pulse NMR experimental methods for the analysis of vegetable oils.

In this work, we describe the experiments for the detection of ammonium nitrate (AN) with a toroidal RF probe with an effective detection volume of 137.5 L. The system includes a Tecmag Scout NQR console, a Tomco linear power amplifier (4 kW), a duplexer and a high-power Q-factor spoiler. We studied the influence of partial metal shielding with an aluminium foil as well as the inclusion of metal pieces in an AN sample on the detection of the AN NQR signal. We have also tested NQR detection of AN placed in the open box made of soft iron plates. We have shown that the detection of the NQR signal of AN in the configurations where there is a hole in the shield around the AN sample is possible.

As a result of enormous progress in nanoscale electronics, interest in artificial intelligence (AI) supported systems has also increased greatly. These systems are typically designed to process computationally intensive data. Parallel processing neural network architectures are particularly noteworthy for their ability to process dense data at high speeds, making them suitable candidates for AI algorithms. Due to their ability to combine processing and memory functions in a single device, memristors offer a significant advantage over other electronic platforms in terms of area scaling efficiency and energy savings. In this study, single-layer and bilayer metal-oxide HfOx and TiOy memristor devices inspired by biological synapses were fabricated by pulsed laser and magnetron sputtering deposition techniques in high vacuum with different oxide thicknesses. The structural and electrical properties of the fabricated devices were analysed using x-ray reflectivity, x-ray photoelectron spectroscopy, and standard two-probe electrical characterization measurements. The stoichiometry and degree of oxidation of the elements in the oxide material for each thin film were determined. Moreover, the switching characteristics of the metal oxide upper layer in bilayer devices indicated its potential as a selective layer for synapse. The devices successfully maintained the previous conductivity values, and the conductivity increased after each pulse and reached its maximum value. Furthermore, the study successfully observed synaptic behaviours with long-term potentiation, long-term depression (LTD), paired-pulse facilitation, and spike-timing-dependent plasticity, showcasing potential of the devices for neuromorphic computing applications.

The paper focuses on exploring the left-handed microwave properties of a double negative metamaterial formed by utilizing elements from two natural materials: (a) thin-layer ferrite, which exhibits effective negative permeability, and (b) thin-layer TiO2 (memristor), which exhibits effective negative permittivity. Both of these natural materials possess negative constitutive parameters within the frequency band where they exhibit left-handed properties. We have defined the conditions under which a backward wave appears in the double negative frequency band. We analyze a left-handed metamaterial (LHM) for the microwave frequency band formed by a multilayer structure from the above-mentioned materials. We have theoretically demonstrated the transparency of this LHM. Furthermore, we demonstrate the ability to control the electromagnetic properties of the metamaterial. This can be achieved not only by applying both static magnetic and static electric fields but also by solely using a static electric field. The latter is one of the main advantages of this structure for technological implementation. We discuss potential applications of the designed structure as a component of microwave electronics. The capability to control various resistance states of nanoscaled TiOX with low voltage offers further control over the properties of the left-handed metamaterial.

Cobalt-rich Co_(1-x)Ge_x alloy thin films with various Ge concentrations (up to x = 0.09 ) have been investigated by vibrating sample magnetometry and ferromagnetic resonance techniques to understand the influence of Ge doping on magnetostatic and magnetodynamic properties. Room-temperature magnetization curves have shown that the addition of Ge atoms can reduce the saturation magnetization in a fast manner. Utilizing a conventional ferromagnetic resonance setup, the out-of-plane angular dependencies of the resonance spectra have been measured and data have been analyzed using a computer program to simulate the magnetic behavior of the thin-film alloys. The experimental findings demonstrate that the magnetic properties of Co_(1-x)Ge_x alloys can be precisely adjusted by varying the Ge content. Both the g-factor and the Gilbert-damping parameter show correlated changes, highlighting the tunability of these magnetic characteristics. This ability to modify saturation magnetization and damping parameters by altering the Ge concentration enables the optimization and customization of the alloy for specific applications in spintronic devices.

In this work, we show that the magnetostatic (MS) magnon modes (i.e., the spinwaves with wavelengths much larger than the exchange length), which are excited as a result of the coupling between the 2D microwave resonator and the YIG crystal, can be efficiently modeled by use of finite element method software (e.g., CST Studio Suite or Comsol MP). Yttrium iron garnet (YIG) has been used as a model material, which is a ferrimagnetic insulator transparent not only to MW but also to optical and telecommunication frequencies. It also has a very low damping parameter — a property advantageous from the point of view of potential applications. However, this benefit turns out in an issue in the FEM modeling because of the very high non-linearity in the EM properties of YIG near resonances due to uniform or MS modes. We found that it is possible to accelerate the FEM calculations by artificially increasing the damping constant of the model material (YIG). Our FEM modeling studies reveal an excellent agreement with experimental results. In full agreement with experimental data, our modeling study reveals a strong coupling between the YIG crystal and the microwave resonator, observed in the dispersion curves of the modes. We demonstrate the realization of the strong coupling regime, which is especially important for HQS implementations.

An inherently low signal-to-noise ratio of the NQR technique limits the application of this technique to the cases where the detection of large quantities of nitrogen-based substances is required (e.g., bombs placed under a road or in a vehicle). NQR detection of nitrogen-based substances at a distance or in a partially shielded volume faces the problem of manipulation with high excitation powers. To achieve the high signal-to-noise ratio (SNR), required for reliable detection of NQR signals, the quality factor (Q) of the resonant circuit should be as high as possible. However, the high Q-factor leads to a prolongation of the transient process in the resonant LC circuit, because after the application of powerful RF excitation pulses, unwanted oscillations occur in the RF probe, which should be suppressed before the registration of an NQR signal. This paper presents a method for the suppression of transient processes in a nuclear quadrupole resonance RF sensor. Operation of the device in the low-frequency range of 0.5–1MHz and RF pulse powers up to 4kW is considered. The design allows operation with a high-quality (≥200) resonant circuit and high voltages (several kilovolts) in the sensor. If necessary, the circuit can be easily scaled to higher voltages or currents in the resonant circuit.

High mobility and the absence of the skyrmion Hall effect are demonstrated in a magnetic skyrmionium, which consists of two skyrmions with opposite topological charges. Despite these advantages, material defects have the potential to alter the skyrmionium's dynamics. In this report, we investigate the motion of a skyrmionium driven by a current on a racetrack containing an engineered cylindrical defect. Our model demonstrates three possible outcomes of the interaction between the skyrmionium and the defect, depending on the applied current density: pinning, transformation, and transmission. Pinning takes place when the driving force generated by the current is inadequate to counteract the repulsive force at the defect boundary, causing the skyrmionium to become entrapped. Transformation happens inside the defect, where the skyrmionium might convert into a skyrmion due to the higher effective field resulting from the change in film thickness. Transmission takes place when the force exerted by the applied current significantly exceeds the repulsive force at the defect boundary, leading to minimal impact on the skyrmionium motion. These results offer significant understanding of skyrmionium behavior when interacting with engineered defects and present potential implications for the development of novel skyrmionic devices.

Nowadays, remarkable progress has been observed in research into neuromorphic computing systems inspired by the human brain. A memristive device can behaviorally imitate the biological neuronal synapse therefore memristor-based neuromorphic computing systems have been proposed in recent studies. In this study, the memristive behaviors of titanium dioxide sandwiched between two platinum electrodes were investigated. For this purpose, three SiO _2 /Pt/TiO _x /Pt thin films with 7.2 nm, 40 nm, and 80 nm TiO _x metal-oxide layers were fabricated using a pulsed laser deposition technique. The fabrication process, structural properties, photoluminescence properties and electrical transport characterization of each thin film have been investigated. All thin films were analyzed in terms of the film stoichiometry and degree of oxidation using high-resolution x-ray photoelectron spectroscopy. By measuring the layer thickness, density, and surface roughness with the x-ray reflectivity technique, by analyzing the structural defects with photoluminescence spectroscopy and by characterizing the quasi-static electrical properties with the conventional two probes technique, we have shown that the fabricated memristive devices have bipolar digital switching properties with high R _OFF /R _ON ratio. This type of switching behavior is applicable in random access memories. Experimental current–voltage behavior in the form of pinched hysteresis loop of the films have been modelled with generalized memristor model.

The magnetic properties of Pt/CoFeTaB/Ir and Ir/CoFeTaB/Pt trilayer thin films have been studied using angular- and temperature-dependent ferromagnetic resonance. This enables quantitative determination of the various contributions to the magnetic behavior, including separating, the effective Gilbert damping, inhomogeneous damping, and two-magnon-scattering contributions to the magnetic dissipation. As-deposited films show behavior consistent with significant incorporation of Ir into CoFeTaB only when the Ir layer is deposited first. Annealing of the structures at 300 ^∘C causes only minor structural and magnetic modification when Pt is deposited first, and more pronounced changes, attributed to thermally-driven out-diffusion of Ir from CoFeTaB, are found when Ir is deposited first. A holistic consideration of the magnetic resonance behavior can provide detailed information on the atomic-scale structure in magnetic thin-film devices.

Hybrid Quantum Systems (HQS), consisting of microwave (MW) and optic subsystems interacting through a magnon interface, have attracted the remarkable attention of researchers because of the very intriguing basic physics involved and many potential applications in various fields of quantum technology (e.g., quantum transduction and communication). It has been already shown that a strong coupling between the Yttrium Iron Garnet (YIG) sphere and the 3D microwave resonator with a formation of the Cavity-Magnon-Polariton (CMP) is achievable. Recently, the systems based on the use of planar (2D) MW resonators and YIG crystals or films have attracted research attention because they are very interesting from the point of view of their integration with the quantum circuits based on planar superconducting elements. It has been already shown that a strong coupling regime in 2D systems can be also obtained. Furthermore, the novel physics observed in the planar geometries is believed to provide a platform for the realization of many other applications, for instance, in highly sensitive RF/MW sensors. In this work, the state of the art of HQSs based on magnon materials is briefly reviewed. Approaches for analyzing and modeling these systems and their applicability for the various configurations are discussed. Finite Element Method (FEM) simulations of the hybrid magnon systems, consisting of MW resonators and YIG crystals (for scales larger than the exchange length) are demonstrated to provide a powerful tool for the analysis of these systems. An example of the experimental realization of HQSs based on the planar MW resonator coupled to the magnetic resonance mode of the YIG thin film is given. A good agreement between the experimental and modeling results reveals that FEM simulations are a powerful tool for the analysis of these systems in the case of the HQS scale larger than the magnon-material exchange length.

We report the development and test of planar microwave Inverse Anapole Resonators (IARs) made of superconducting Yttrium Barium Copper Oxide (YBCO) for electron spin resonance spectroscopy on small samples. We first characterize our resonators in zero field and then by carrying out transmission spectroscopy on a diluted $$\alpha ,\gamma $$ -bisdiphenylene- $$\beta $$ -phenylally (BDPA) organic radical spin ensemble in an applied magnetic field. These IARs allow us to carry out electron spin resonance spectroscopy both in continuous-wave and pulsed-wave mode, and to estimate the spin memory time of BDPA. The comparison with the results obtained for the same sample on typical linear coplanar resonators shows an improvement by $$\approx 2\text { - up to}\,3$$ – orders of magnitude in spin sensitivity, with effective sensing volumes below 1 nanoliter. The best sensitivity we achieved is $$S\approx \,10^{7}\,\text {spin}/\sqrt{\mathrm{Hz}}$$ in the pulsed-wave regime. These results compare well with similar experiments reported in the literature.

The analysis of edible oils, which have an important place in human health, is very significant. One of the most widely used edible oil is olive oil, which unfortunately is very frequently adulterated by adding a different, cheaper oil to reduce its cost. Therefore, a useful and economical method or device is needed to detect counterfeiting and adulteration of oils. In this study, a low-cost, easy-to-use, lightweight, and practical time-domain nuclear magnetic resonance (TD-NMR) device was developed for quality control and food safety applications, including testing edible oils. For this purpose, a measurement system, consisting of an O-shaped magnet with NdFeB permanent disc magnets, a radio frequency (RF) detection probe and a temperature stabilization/control system, was designed. Using this homemade device, the spin–lattice ( T 1 ) and spin–spin ( T 2 ) relaxation times of seven different olive oils were measured. The received results were compared with those obtained by two different commercial low-field NMR (LF-NMR) devices. It was established a good agreement between the experimental results obtained on the homemade system and the commercial LF-NMR devices. Detection of various grades of olive oil, as well as oil adulteration, was demonstrated for a set of different olive oils and a mixture of olive and sunflower oils using the developed homemade TD-NMR device.

In this work, we describe the design of a sensing system for the NQR detection of nitrogen substances in a large inspection volume. The system consists of a Tecmag Scout NQR console, Tomco linear amplifier (4kW), a large distance/volume RF probe (either planar gradiometer or toroidal coil), a duplexer and a high-power Q-factor spoiler. We studied the conditions for optimal unilateral detection at distances up to 20 cm as well as for the detection inside a large volume. It has been shown that depending on RF probe configuration and ambient RF noise level), a $14_\mathrm{N}$ NQR signal of a small amount (100 g) of hexamethylenetetramine (HMT) as the reference nitrogen substance can be detected using both types of RF detectors. Furthermore, a possibility of NQR detection for a partially shielded HMT sample has been also shown. The influence of conducting bodies near an NQR sample for detection performance has been studied as well. We have also demonstrated that this system can be applied to the detection of ammonium nitrate.

NMR measurements in low and ultra-low magnetic fields can become a way to distinguish organic liquids. The spectral splitting in the NMR spectra taken at very low fields is due to indirect spin-spin interaction (J-coupling), while no chemical shift information is usually available. Therefore, J-splittings are the only effect that distinguishes spectra in a low field. In this work, Earth's magnetic field NMR-spectra from three various organophosphorus substances have been measured using low-cost equipment. We have shown that the EF-NMR spectra of various liquids with similar structures are significantly different from each other. The analysis of spectra has been carried out and the results are compared with the literature data.