Study explores influence of duration-of-thermal-treatment for tuning structural,magnetic,dielectric response of nano-MgFe2O4 produced via sol-gel-auto-ignition. XRD(X-ray-diffraction) confirms nano-crystalline-spinel-phase growth, grain sizes ranging from 25.3 to 49.3 nm following annealing at 500 °C for 1–3 hours. Structural analysis reveals a non-monotonic variation in lattice parameter, and progressive grain growth. Magnetic characterization indicates enhanced A-A, A-B super-exchange-interaction, weakened B-B exchange, leading to decreased Néel magnetic moment. Cation redistribution shows, increased Mg²⁺,reduced Fe³⁺ at the B-site, altering the oxygen positional parameter and inversion degree. EDS validates that Fe,Mg,O are present in the studied samples. SEM images confirm particle-aggregation, irregular size- dispersal of particles, owing to samples’-magnetic-nature. Mössbauer-spectroscopy reveals two-magnetic-sextets corresponding to Fe³⁺-ions at A,B-sites, with isomer-shift confirming +3 oxidation-state. Non-magnetic-doublet(~23%), attributed to spin-disordered-shell-region. Frequency-dependent-dielectric-measurements show decreasing-dielectric-constant(ε′,ε″),losses, while AC-conductivity(σac) increases notably, follows power-law behavior. Impedance-analysis show grain-boundaries govern high-frequency-dielectric-response. Thermal annealing time–controlled evolution of structural,magnetic,dielectric properties indicates suitability of Mg-nanoferrites for microwave-device-applications.

Magnetoelectric materials are one of the potential candidates that can counter the growing need of low‐power memory and spintronic devices due to their ability to electrically control magnetic states. Manipulation of a magnetic state with the sole use of an electric field has faced several challenges like volatility and non‐reproducibility. Here, we propose a magnetostrictive FeGa thin film interfaced with a relaxor ferroelectric substrate (PMN‐PT) having a [011] surface cut. The polarization rotation is controlled near the coercive electric fields and stabilized at remanence, which generates distinct strained states. This strain transfers to the FeGa layer mechanically, inducing a net rotation of magnetization without the need of any bias magnetic field applicators. Imaging of the magnetic domains reveals spatial and real‐time information about its variation and adds insight on the modification of magnetic anisotropy. The newly created magnetic information can be erased by reaching ferroelectric saturation and subsequently regenerated through specific electrical pulses. These results demonstrate the possibility of manipulating the magnetization via controlled polarization rotation, for use in strain‐driven magneto‐electronics.

This study focuses on the synthesis and characterization of advanced polymeric composite electrospun nanofibers (NFs) containing magnetic oxide nanoparticles (NPs). By leveraging the method of electrospinning, the research aims to investigate polymer composites with enhanced interfacial properties, improved double-layer capacitance, and adequate biocompatibility. Electrospun polyacrylonitrile (PAN) NFs embedded with Fe₂O₃ and MnZn-Ferrite NPs were comprehensively characterized using advanced techniques, i.e., Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, high-resolution scanning electron microscopy, X-ray diffraction, and alternating gradient field magnetometry. The incorporation of metal oxide NPs led to significant changes in the thermal, spectroscopic, and morphological properties of the NFs. Spectroscopic analysis confirmed increased oxidation, graphitic carbon content, and the formation of new nitrogen functionalities after heat treatment. Furthermore, interactions between nitrile groups and metal ions were observed, indicating the influence of nanoparticles on surface chemistry. Magnetic characterization demonstrated the potential of these composite NFs to generate magnetic fields for biomedical manipulation. Cytocompatibility studies revealed no significant impact on the viability or morphology of human mesenchymal stromal cells, highlighting their biocompatibility. These findings suggest the promising use of PAN-magnetic NFs in applications including targeted drug administration, magnetic resonance imaging, and magnetic hyperthermia for cancer treatment.

This study focuses on the synthesis and characterization of advanced polymeric composite electrospun nanofibers (NFs) containing magnetic oxide nanoparticles (NPs). By leveraging the method of electrospinning, the research aims to investigate polymer composites with enhanced interfacial properties, improved double-layer capacitance, and adequate biocompatibility. Electrospun polyacrylonitrile (PAN) NFs embedded with Fe2O3 and MnZn ferrite NPs were comprehensively characterized using advanced techniques, i.e., Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), high-resolution scanning electron microscopy (HR-SEM), X-ray diffraction (XRD), and alternating gradient field magnetometry (AGFM). The incorporation of metal oxide NPs led to significant changes in the thermal, spectroscopic, and morphological properties of the NFs. XPS analysis confirmed increased oxidation, graphitic carbon content, and the formation of new nitrogen functionalities after heat treatment. Furthermore, interactions between nitrile groups and metal ions were observed, indicating the influence of nanoparticles on surface chemistry. Magnetic characterization demonstrated the potential of these composite NFs to generate magnetic fields for biomedical manipulation. Cytocompatibility studies revealed no significant impact on the viability or morphology of human mesenchymal stromal cells, highlighting their biocompatibility. These findings suggest the promising use of PAN-magnetic NFs in applications including targeted drug administration, magnetic resonance imaging (MRI), and magnetic hyperthermia for cancer treatment.

A low-cost Nanoporous Gold (NPG) has been successfully prepared by chemical dealloying of a Au33Fe67 supersaturated solid solution, whose ribbons were obtained by rapid solidification using melt-spinning technique. The dealloying procedures were carried out in 1M HNO3 at 70 °C for varying durations. As-quenched ribbon and dealloyed samples have been structurally and compositionally investigated using XRD, FESEM and EDS techniques. The obtained NPG is homogeneous with tunable ligament size and shape, easy-to-handle and free-standing. Most notably, a metastable precursor has been favourably obtained from an immiscible Au-Fe system. Furthermore, according to the characterization results, a mechanism of dealloying has been proposed. Pairing Au with cheap and abundant Fe and fabricating an Fe-rich precursor gives an exceedingly cost-effective starting material. No usage of critical raw materials is involved. Then, employing a straight-forward and rapid dealloying procedure to obtain the NPG sample, makes for an overall inexpensive and sustainable production.

Magnetically responsive soft biomaterials are at the forefront of bioengineering and biorobotics. We have created a magnetic hybrid material by coupling silk fibroin─i.e., a natural biopolymer with an optimal combination of biocompatibility and mechanical robustness─with the FeCo alloy, the ferromagnetic material with the highest saturation magnetization. The material is in the form of a 6 μm-thick silk fibroin film, coated with a FeCo layer (nominal thickness: 10 nm) grown by magnetron sputtering deposition. The sputtering deposition technique is versatile and eco-friendly and proves effective for growing the magnetic layer on the biopolymer substrate, also allowing one to select the area to be decorated. The hybrid material is biocompatible, lightweight, flexible, robust, and water-resistant. Electrical, structural, mechanical, and magnetic characterization of the material, both as-prepared and after being soaked in water, have provided information on the adhesion between the silk fibroin substrate and the FeCo layer and on the state of internal mechanical stresses. The hybrid film exhibits a high magnetic bending response under a magnetic field gradient, thanks to an ultralow fraction of the FeCo component (less than 0.1 vol %, i.e., well below 1 wt %). This reduces the risk of adverse health effects and makes the material suitable for bioactuation applications.

The detection of magnetic nanoparticles in a liquid medium and the quantification of their concentration have the potential to improve the efficiency of several relevant applications in different fields, including medicine, environmental remediation, and mechanical engineering. To this end, sensors based on the magneto-impedance effect have attracted much attention due to their high sensitivity to the stray magnetic field generated by magnetic nanoparticles, their simple fabrication process, and their relatively low cost. To improve the sensitivity of these sensors, a multidisciplinary approach is required to study a wide range of soft magnetic materials as sensing elements and to customize the magnetic properties of nanoparticles. The combination of magneto-impedance sensors with ad hoc microfluidic systems favors the design of integrated portable devices with high specificity towards magnetic ferrofluids, allowing the use of very small sample volumes and making measurements faster and more reliable. In this work, a magneto-impedance sensor based on an amorphous Fe73.5Nb3Cu1Si13.5B9 wire as the sensing element is integrated into a customized millifluidic chip. The sensor detects the presence of magnetic nanoparticles in the ferrofluid and distinguishes the different stray fields generated by single-domain superparamagnetic iron oxide nanoparticles or magnetically blocked Co-ferrite nanoparticles.

Magnetic measurements are vital to support European challenges in areas such as electric vehicles; health; power transformation and harvesting; clean, affordable and secure energy; information and sensor technology. However, only very few European NMIs have the capabilities to perform traceable measurements of all of the most important magnetic quantities. Consequently, the adoption of novel technologies and materials is hindered by the lack of local metrological expertise that research and development activities in academia and industry could exploit. A European project (TRaMM, 21SCP02), in the framework of the Small Collaborative Projects (SCP) call 2021, aimed at transferring the expertise of INRIM (Italy) in the field of magnetic calibration and measurements to CEM (Spain) and NSAI (Ireland), and to interested stakeholders.

Magnetostrictive materials are essential components in sensors, actuators and energy storage devices due to their unique ability to convert mechanical stress into changes in magnetic properties and vice versa. However, their conventional operation typically requires physical contact to apply stress or relies on permanent magnets and coils to control magnetic properties. This poses significant limitations and has hindered miniaturization of devices and their integration into contactless technologies. Here, we report on a novel approach that overcomes these limitations by using light to transfer mechanical stress to a magnetostrictive device, thereby achieving non-contact and reversible opto-mechanical control of its magnetic and electrical properties. Our solution combines a magnetostrictive Fe70Ga30 thin film with a Liquid Crystalline Network responsive to UV and visible light. Magnetic properties can be modulated by changing the wavelength of the light and time of illumination. Remarkably, the stable shape change of the LCN induced by light leads to the retention of magnetic properties even after the light is switched off, resulting in a magnetic memory effect with an advantage in terms of energy consumption compared to the use of conventional magnetic field applicators. The memory effect is erased by visible light, which releases the mechanical stress in the photoresponsive layer. Therefore, this new composite material creates a fully reconfigurable magnetic system controlled by light.

In this paper, we have studied the effect on the structure and magnetic properties of partial Pd substitution by Gd in Fe–Pd thin films of nominal composition Fe56Pd44−xGdx (x = 1, 3, 5, and 7), deposited onto Si(100) and Si(100)/SiO2 substrates by thermal evaporation. Several techniques contribute to the characterization of their microstructure and magnetic properties, such as x-ray diffraction (XRD), scanning electron microscopy, alternating gradient field magnetometry, and magnetic force microscopy (MFM). X-ray diffraction shows that the as-deposited films are either amorphous or contain a disordered FePd phase, depending on the film thickness. The transformation of disordered fcc-FePd into ordered fct-FePd has been induced by a heat treatment at 530 °C for 4 h. The addition of gadolinium leads to a reduction in the coercivity as a consequence of the emergence of soft phases and of the progressive reduction of the fct-FePd phase, which is primarily responsible for the observed maze magnetic domains. The exchange coupling between the soft phase and the hard fct-FePd phase is demonstrated by first-order reversal curves (FORCs).

Magnetostrictive materials are essential components in sensors, actuators, and energy-storage devices due to their ability to convert mechanical stress into changes in magnetic properties and vice-versa. However, their operation typically requires physical contact to apply stress or relies on magnetic field sources to control magnetic properties. This poses significant limitations to devices miniaturization and their integration into contactless technologies. This work reports on an approach that overcomes these limitations by using light to transfer mechanical stress to a magnetostrictive device, thereby achieving non-contact and reversible opto-mechanical control of its magnetic and electrical properties. The proposed solution combines a magnetostrictive Fe70Ga30 thin film with a photo-responsive Liquid Crystalline Network (LCN). Magnetic properties are modulated by changing the light wavelength and illumination time. Remarkably, the stable shape change of the LCN induced by ultraviolet (UV) light leads to the retention of magnetic properties even after the light is switched off, resulting in a magnetic memory effect with an energy consumption advantage over the use of conventional magnetic field applicators. The memory effect is erased by visible light, which releases the mechanical stress in the photoresponsive layer. Therefore, this new composite material creates a fully reconfigurable magnetic system controlled by light.

Artificial magnetoelectric materials possess huge potential to be utilized in the development of energy efficient spintronic devices. In the past decade, the search for a good ferromagnetic/ferroelectric combination having the ability to create high magnetoelectric coupling, created new insights and also new challenges. In this report, the magnetoelectric effect is studied in the FeGa/PMN-PT(001) multiferroic heterostructures in the presence of electric fields via strain-mediated effects. The formation of magnetic anisotropy in FeGa is observed after changing the polarization of PMN-PT to out-of-plane orientations. The magnetic domain structures forming during the magnetization reversal were studied in compressive, tensile and remanent strained states. The changes in the magnetic properties were reversible after each cycling of the electric field polarity, hence creating a non-volatile system. The control of magnetization switching sustained by an ON–OFF electric field makes our multiferroic heterostructure suitable for application in low-power magnetoelectric based memory applications.

Dense and mesoporous FePd nanowires (NWs) with 45 to 60 at.% Pd content were successfully fabricated by template- and micelle-assisted pulsed potentiostatic electrodeposition using nanoporous anodic alumina and polycarbonate templates of varying pore sizes. An FePd electrolyte was utilized for obtaining dense NWs while a block copolymer, P-123, was added to this electrolyte as the micelle-forming surfactant to produce mesoporous NWs. The structural and magnetic properties of the NWs were investigated by electron microscopy, X-ray diffraction, and vibrating sample magnetometry. The as-prepared NWs were single phase with a face-centered cubic structure exhibiting 3.1 µm to 7.1 µm of length. Mesoporous NWs revealed a core-shell structure where the porosity was only witnessed in the internal volume of the NW while the outer surface remained non-porous. Magnetic measurements revealed that the samples displayed a soft ferromagnetic behavior that depended on the shape anisotropy and the interwire dipolar interactions. The mesoporous core and dense shell structure of the NWs were seen to be slightly affecting the magnetic properties. Moreover, mesoporous NWs performed excellently as SERS substrates for the detection of 4,4′-bipyridine, showing a low detection limit of 10−12 M. The signal enhancement can be attributed to the mesoporous morphology as well as the close proximity of the embedded NWs being conducive to localized surface plasmon resonance.

Magnetic hyperthermia is an oncological therapy that exploits magnetic nanoparticles activated by radiofrequency magnetic fields to produce a controlled temperature increase in a diseased tissue. The specific loss power (SLP) of magnetic nanoparticles or the capability to release heat can be improved using surface treatments, which can reduce agglomeration effects, thus impacting on local magnetostatic interactions. In this work, Fe3O4 nanoparticles are synthesized via a coprecipitation reaction and fully characterized in terms of structural, morphological, dimensional, magnetic, and hyperthermia properties (under the Hergt- Dutz limit). Different types of surface coatings are tested, comparing their impact on the heating efficacy and colloidal stability, resulting that sodium citrate leads to a doubling of the SLP with a substantial improvement in dispersion and stability in solution over time; an SLP value of around 170 W/g is obtained in this case for a 100 kHz and 48 kA/m magnetic field.

In this paper we have studied the effect on the structure and magnetic properties of partial Pd substitution by Gd in Fe-Pd thin films of nominal composition Fe56Pd44-xGdx (x = 1, 3, 5 and 7), deposited onto Si(100) and Si(100)/SiO2 substrates by thermal evaporation. Several techniques contribute to the characterisation of their microstructure and magnetic properties, such as, X-ray diffraction (XRD), scanning electron microscopy (SEM), alternating gradient field magnetometry (AGFM), magnetic force microscopy (MFM). The X-ray diffraction shows that the as-deposited films are either amorphous or contain a disordered FePd phase, depending on film thickness. The transformation of disordered fcc-FePd into ordered fct-FePd has been induced by a heat treatment at 530 °C for 4 hours. The addition of gadolinium leads to a reduction of the coercivity as a consequence of emergence of soft phases and of the progressive reduction of the fct-FePd phase which is primarily responsible for the observed maze magnetic domains. The exchange coupling between the soft phase and the hard fct-FePd phase is demonstrated by first-order reversal curves (FORC).

Magnetic vortices have been an interesting element in the past decades due to their flux-closure domain structures which can be stabilized at ground states in soft ferromagnetic microstructures. In this work, vortex states are shown to be nucleated and stabilized in Fe80Ga20 and Fe70Ga30 disks, which can be an upcoming candidate for applications in strain-induced electric field control of magnetic states owing to the high magnetostriction of the alloy. The magnetization reversal in the disks occurs by the formation of a vortex, double vortex or S-domain state. Micromagnetic simulations have been performed using the FeGa material parameters and the simulated magnetic states are in good agreement with the experimental results. The studies performed here can be essential for the use of FeGa alloy in low-power electronics.

The connection of multidisciplinary and versatile techniques capable of depositing and modeling thin films in multistep complex fabrication processes offers different perspectives and additional degrees of freedom in the realization of patterned magnetic materials whose peculiar physical properties meet the specific needs of several applications. In this work, a fast and cost-effective dealloying process is combined with a fast, low-cost, scalable electroless deposition technique to realize hybrid magnetic heterostructures. The gold nanoporous surface obtained by the dealloying of an Au40Si20Cu28Ag7Pd5 ribbon is used as a nanostructured substrate for the electrodeposition of cobalt. In the first steps of the deposition, the Co atoms fill the gold pores and arrange themselves into a patterned thin film with harder magnetic properties; then they continue their growth into an upper layer with softer magnetic properties. The structural characterization of the hybrid magnetic heterostructures is performed using an X-ray diffraction technique and energy-dispersive X-ray spectroscopy, while the morphology of the samples as a function of the electrodeposition time is characterized by images taken in top and cross-section view using scanning electron microscopy. Then, the structural and morphologic features are correlated with the room-temperature magnetic properties deduced from an alternating-gradient magnetometer's measurements of the hysteresis loop and first order reversal curves.

We study the magnetic properties of arrays of Co nanowires which exhibit zero bias-field ferromagnetic resonance absorptions in a 0–30 GHz range. Columnar arrays of Co nanowires with lengths of 8–15 µm were electrochemically grown using ∼20 µm thick anodic alumina membranes with 50 nm pore diameters. Microstructural, static magnetic, and microwave properties of five different nanowire arrays were characterized. The studied Co nanowires present different crystal structure textures and magnetic properties. The static magnetic loop shapes and the ferromagnetic resonance frequencies of the nanowire arrays were correctly reproduced using the Mumax3 micromagnetic software. For each sample input parameters dependent on the x-ray diffraction and microstructural data, were fine-tuned to allow the best fit of the experimental hysteresis loops and the related microwave spectra. Using this method, it was possible to analyze the rather complex interplay between geometry and magneto-structural features of the different arrays, defining which parameters play a key role in the development of nano-systems with specific microwave properties.

The study of the status of the marine environment is typically carried out by monitoring several parameters, both chemical and physicochemical, classified as Essential Ocean Variables by the Global Climate Observing System. These variables are useful to obtain quantifiable indications to monitor the phenomena occurring in the oceans and to relate them to the changes occurring on the global scale in all the environmental compartments. In this framework, a research collaboration is ongoing between the Italian National Metrology Institute (INRiM) and the Italian National Agency for New Technologies, Energy and Sustainable Economic Development (ENEA), to support the collection, validation and maintenance of reliable and accurate databases, by applying the concepts of metrology from the laboratory to the field. Among the main Essential Ocean Variables, the dissolved oxygen and the partial pressure of carbon dioxide are key parameters to monitor the changing ocean and are largely measured in stations around the globe. INRiM and ENEA are collaborating in the measurement of these variables, focusing on the metrological traceability issues and the measurement uncertainty evaluation, also exploiting innovative Internet of Underwater Things (IoUT) in situ monitoring systems developed by WSense, spinoff of Sapienza University.

Electronics and soft robotics demand the development of a new generation of hybrid materials featuring novel properties. Among these, remarkable mechanical properties are required to sustain mechanical stresses, and electrical and magnetic properties are essential to design the devices’ interface. In this study, a hybrid material is presented, consisting of a spider silk thread, providing mechanical robustness, coated with a layer of a magnetostrictive FeCo alloy, which ensures both electrical conductivity and stress‐sensitive magnetic properties. The durability and the homogeneity of the composite are validated, as well as its ability to respond to magnetic and mechanical stimuli. Despite the coating, the soft nature of the silk and its mechanical performances are preserved. The magnetic study reveals that the magnetic behavior of the film is strongly affected by the silk thread–FeCo layer interaction, especially under mechanical stresses. Indeed, when the composite is subjected to tensile strain, the magnetic signal changes accordingly, indicating that the layer–silk interaction is maintained and can be exploited to reveal the tensional state of the sample even under severe cycles. Therefore, the presented hybrid material is a flexible fiber with properties that are suitable for magneto‐electronics applications, e.g., magnetic actuators as well as strain/stress sensors.