Magnetoimpedance in symmetric and non-symmetric nanostructured multilayers: A theoretical study

Intensive studies of the magnetoimpedance (MI) effect in nanostructured multilayers provide a good phenomenological basis and theoretical description for the symmetric case when top and bottom layers of ferromagnet/conductor/ferromagnet structure have the same thickness and consist of one magnetic layer each. At the same time, there is no model to describe the MI response in multilayered films. Here, we propose the corresponding model and analyze the influence of the multilayer parameters on the field and frequency dependences of the MI. The approach is based on the calculation of the field distribution within the multilayer by means of a solution of lineralizied Maxwell equations together with the Landau–Lifshitz equation for the magnetization motion. The theoretical model developed allows one to explain qualitatively the main features of the MI effect in multilayers and could be useful for optimization of the film parameters. It might also be useful as a model case for the development of MI magnetic biosensors for magnetic biomarker detection. © 2019 by the authors. Licensee MDPI, Basel, Switzerland.Russian Science Foundation: 18-19-00090Funding: This research was funded by the Russian Science Foundation, grant number 18-19-00090

Off-diagonal magnetoimpedance in field-annealed Co-based amorphous ribbons

The off-diagonal magnetoimpedance in field-annealed CoFeSiB amorphous ribbons was measured in the low-frequency range using a pick-up coil wound around the sample. The asymmetric two-peak behavior of the field dependence of the off-diagonal impedance was observed. The asymmetry is attributed to the formation of a hard magnetic crystalline phase at the ribbon surface. The experimental results are interpreted in terms of the surface impedance tensor. It is assumed that the ribbon consists of an inner amorphous region and surface crystalline layers. The coupling between the crystalline and amorphous phases is described through an effective bias field. A qualitative agreement between the calculated dependences and experimental data is demonstrated. The results obtained may be useful for development of weak magnetic-field sensors.Comment: 19 pages, 6 figure

A Model for the Magnetoimpedance Effect in Non-Symmetric Nanostructured Multilayered Films with Ferrogel Coverings

Magnetoimpedance (MI) biosensors for the detection of in-tissue incorporated magnetic nanoparticles are a subject of special interest. The possibility of the detection of the ferrogel samples mimicking the natural tissues with nanoparticles was proven previously for symmetric MI thin-film multilayers. In this work, in order to describe the MI effect in non-symmetric multilayered elements covered by ferrogel layer we propose an electromagnetic model based on a solution of the 4Maxwell equations. The approach is based on the previous calculations of the distribution of electromagnetic fields in the non-symmetric multilayers further developed for the case of the ferrogel covering. The role of the asymmetry of the film on the MI response of the multilayer–ferrogel structure is analyzed in the details. The MI field and frequency dependences, the concentration dependences of the MI for fixed frequencies and the frequency dependence of the concentration sensitivities are obtained for the detection process by both symmetric and non-symmetric MI structures.This research was funded by the University Basque Country UPV/EHU, Research Groups Funding (IT1245-19)

Magnetoimpedance in Symmetric and Non-Symmetric Nanostructured Multilayers: A Theoretical Study

Intensive studies of the magnetoimpedance (MI) effect in nanostructured multilayers provide a good phenomenological basis and theoretical description for the symmetric case when top and bottom layers of ferromagnet/conductor/ferromagnet structure have the same thickness and consist of one magnetic layer each. At the same time, there is no model to describe the MI response in multilayered films. Here, we propose the corresponding model and analyze the influence of the multilayer parameters on the field and frequency dependences of the MI. The approach is based on the calculation of the field distribution within the multilayer by means of a solution of lineralizied Maxwell equations together with the Landau-Lifshitz equation for the magnetization motion. The theoretical model developed allows one to explain qualitatively the main features of the MI effect in multilayers and could be useful for optimization of the film parameters. It might also be useful as a model case for the development of MI magnetic biosensors for magnetic biomarker detection.This research was funded by the Russian Science Foundation, grant number 18-19-00090

Modeling of torsion stress giant magnetoimpedance in amorphous wires with negative magnetostriction

A model describing the influence of torsion stress on the giant magnetoimpedance in amorphous wires with negative magnetostriction is proposed. The wire impedance is found by means of the solution of Maxwell equations together with the Landau-Lifshitz equation, assuming a simplified spatial distribution of the magnetoelastic anisotropy induced by the torsion stress. The impedance is analyzed as a function of the external magnetic field, torsion stress and frequency. It is shown that the magnetoimpedance ratio torsion dependence has an asymmetric shape, with a sharp peak at some value of the torsion stress. The calculated field and stress dependences of the impedance are in qualitative agreement with results of the experimental study of the torsion stress giant magnetoimpedance in Co-based amorphous wires.Comment: 17 pages, 5 figure

Generation of second harmonic in off-diagonal magneto-impedance in Co-based amorphous ribbons

The off-diagonal magneto-impedance in Co-based amorphous ribbons was measured using a pick-up coil wound around the sample. The ribbons were annealed in air or in vacuum in the presence of a weak magnetic field. The evolution of the first and second harmonics in the pick-up coil voltage as a function of the current amplitude was studied. At low current amplitudes, the first harmonic dominates in the frequency spectrum of the voltage, and at sufficiently high current amplitudes, the amplitude of the second harmonic becomes higher than that of the first harmonic. For air-annealed ribbons, the asymmetric two-peak behaviour of the field dependences of the harmonic amplitudes was observed, which is related to the coupling between the amorphous phase and surface crystalline layers appearing after annealing. For vacuum-annealed samples, the first harmonic has a maximum at zero external field, and the field dependence of the second harmonic exhibits symmetric two-peak behaviour. The experimental results are interpreted in terms of a quasi-static rotational model. It is shown that the appearance of the second harmonic in the pick-up coil voltage is related to the anti-symmetrical distribution of the transverse field induced by the current. The calculated dependences are in a qualitative agreement with the experimental data.Comment: 16 pages, 4 figure

Magnetization reversal process and nonlinear magneto-impedance in Cu/NiFe and Nb/NiFe composite wires

The magnetization reversal of Cu/NiFe and Nb/NiFe composite wires carrying AC current is studied. The frequency spectrum of a voltage induced in a pick-up coil wound around the wire is analyzed. The frequency spectrum is shown to consist of even harmonics within a wide range of AC current amplitudes and longitudinal DC magnetic fields. The strong dependencies of the harmonic amplitudes on the DC field are found. The results obtained may be of importance for the design of weak magnetic field sensors.Comment: 8 pages, 4 figures, publishe

Marine Invertebrate Extracts Induce Colon Cancer Cell Death via ROS-Mediated DNA Oxidative Damage and Mitochondrial Impairment

Marine compounds are a potential source of new anticancer drugs. In this study, the antiproliferative effects of 20 invertebrate marine extracts on three colon cancer cell models (HGUE-C-1, HT-29, and SW-480) were evaluated. Extracts from two nudibranchs (Phyllidia varicosa, NA and Dolabella auricularia, NB), a holothurian (Pseudocol ochirus violaceus, PS), and a soft coral (Carotalcyon sp., CR) were selected due to their potent cytotoxic capacities. The four marine extracts exhibited strong antiproliferative effects and induced cell cycle arrest at the G2/Mtransition, which evolved into early apoptosis in the case of the CR, NA, and NB extracts and necrotic cell death in the case of the PS extract. All the extracts induced, to some extent, intracellular ROS accumulation, mitochondrial depolarization, caspase activation, and DNA damage. The compositions of the four extracts were fully characterized via HPLC-ESI-TOF-MS analysis, which identified up to 98 compounds. We propose that, among the most abundant compounds identified in each extract, diterpenes, steroids, and sesqui- and seterterpenes (CR); cembranolides (PS); diterpenes, polyketides, and indole terpenes (NA); and porphyrin, drimenyl cyclohexanone, and polar steroids (NB) might be candidates for the observed activity. We postulate that reactive oxygen species (ROS) accumulation is responsible for the subsequent DNA damage, mitochondrial depolarization, and cell cycle arrest, ultimately inducing cell death by either apoptosis or necrosis.This research was funded by projects AGL2015-67995-C3-1-R, AGL2015-67995-C3-2-R AGL2015-67995-C3-3-R, RTI2018-096724-B-C21, and 2018-096724-B-C22 from the Spanish Ministry of Science, Innovation and Universities; Project P11-CTS-7625 from Andalusian Regional Government Council of Innovation and Science; projects PROMETEO/2012/007, PROMETEO/2016/006, and VALi+D fellowship (ACIF/2015/158) from Generalitat Valenciana to VR-Tand CIBER (CB12/03/30038, Fisiopatología de la Obesidad y la Nutrición, CIBERobn)