The influence of a ferromagnetic cover layer on giant magnetoimpedance (GMI) effect in nearly-zero magnetostrictive Co66.5Fe3.5Si12.0B18.0 amorphous ribbon after being surface coated by an electrodeposited Co layer of 10 μm in thickness, has been studied in the high frequency range between 10 MHz and 1.5 GHz. Longitudinal MOKE measurements performed on both kind of samples reveal the influence of exchange coupling interaction at the interface between the magnetic amorphous ribbon and electrodeposited Co coating layer, which is sensitive to the skin depth effect at high ac current frequency values. Comparison between GMI responses of the Co coated amorphous ribbon and the as-cast sample is provided. A more sharp and well defined double-peaks dependence of impedance on magnetic field, but with lower peaks intensity, is observed for the Co coated ribbon in the frequency range of 10–100 MHz, while the peaks intensity is higher than that observed in the as-cast ribbon at the high frequency value of 1 GHz due to the higher resistance of the Co electroplated layer than the core one. The influence of a dc bias drive current on the GMI response in both amorphous ribbons (as-cast and Co layered) is analyzed, which originates the removal of magnetic domain structure from both, the as-cast and Co-coated ribbons, giving rise more sensitive GMI effect. CoFeSiB amorphous ribbon with vanishing magnetostriction can achieve improved high frequency magnetic properties after being surface coated with electrodeposited ferromagnetic layers, as outstanding candidates for electromagnetic and magnetomechanical engineering applications.

This work investigates the magnetic and the intrinsic exchange bias (EB) properties of the sol-gel synthesised LaMnO3 and LaFeO3 perovskite compounds. The x-ray diffraction (XRD) has proved the high homogeneity of both compounds, which are crystallised in the orthorhombic Pnma structure (as proved by Rietveld refinement). The field cooling-zero field cooling magnetisation dependent temperature (M(T)) indicates the antiferromagnetic (AFM) nature of these compounds. Nevertheless, an anomalous ferromagnetic (FM) behaviour is observed, which is more likely, arises from the spin canting effect in the Mn3+ and Fe3+ ions. The thermal variation of the magnetisation reciprocal (M-1) has confirmed the presence of this FM component below 110K in LaMnO3 and the Curie-Weiss behaviour above 160K. Also, the magnetic hysteresis loops below 110K are corresponding to the FM-like behaviour. The spin of the FM component couples with the AFM phase spins, leading to the EB effect in both compounds that show maximum values of -11240e and 2343 Oe for the LaMnO3 and LaFeO3 compounds, respectively. It is observed that the EB effect is suppressed with the partial substitution of La3+ by Ba2+ due to the dominance of the FM phase and the absence of the FM/AFM coupling. Also, the influence of the FM-AFM phases co-existence on the magnetocaloric(MCE) properties of the LaMnO3 compound were studied. Where the LaMnO3 compound shows a magnetic entropy change (Delta S) of 0.42 J/kg.K with an adiabatic temperature change (Delta T-ad) of 0.1k that is improved in the La0.8Ba0.2MnO3 compound to 1.3 J/kg.K and 0.4K, respectively. (C) 2020 Elsevier B.V. All rights reserved.

We report on the crystalline structure, morphology and thermomagnetic properties of glass-coated magnetic microwires with Cu 56 Ga 28 Mn 16 composition, as well as the thermal annealing influence on its magneto-structural properties. As-cast CuMnGa microwires exhibit a majority cubic B2 phase, and upon annealing at temperatures up to 573 K a new hexagonal phase appears coexisting with the cubic B2 major phase. Thermal annealing treatments also shift the Curie temperature about 150 K with respect to the one for the as-cast microwire. Furthermore, the signature of a structural phase transition is observed for the microwire annealed at 523 K.

Magnetic entropy change and refrigerant capacity have been determined for a field change of 20 kOe around the second-order magnetic transition of austenite in as-quenched Ni{in51.1}Mn{in31.2}In{in17.7} alloy ribbons produced by melt spinning technique. Samples crystallize in a single-phase austenite with the highly ordered {itL2}{in{it1}}-type crystal structure and a Curie temperature of 275 K. The material shows a maximum magnetic entropy change of % MathType!MTEF!2!1!+- % feaagKart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn % hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr % 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9 % vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x % fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaeyiLdqKaam % 4uamaaDaaaleaacaWGnbaabaGaamyBaiaadggacaWG4baaaOGaeyyp % a0JaeyOeI0IaaGymaiaac6cacaaI3aaaaa!4034! $$\Delta S_M^{max} = - 1.7$$ Jkg{su-1}K{su-1}, an useful working temperature range of 78 K (δ{itT}{in{itFWHM}}) and a refrigerant capacity of {itRC}=132 Jkg{su-1} % MathType!MTEF!2!1!+- % feaagKart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn % hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr % 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9 % vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x % fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaWaaeWaaeaaca % WGsbGaam4qaiabg2da9maaemaabaGaeyiLdqKaam4uamaaDaaaleaa % caWGnbaabaGaamyBaiaadggacaWG4baaaaGccaGLhWUaayjcSdGaae % iEaiaabccacqaH0oazcaWGubWaaSbaaSqaaiaadAeacaWGxbGaamis % aiaad2eaaeqaaaGccaGLOaGaayzkaaaaaa!4AFB! $$\left( {RC = \left| {\Delta S_M^{max}} \right|{\text{x }}\delta {T_{FWHM}}} \right)$$ . The considerable {itRC} value obtained together with the fabrication via a single-step process make austenitic Ni-Mn-In ribbons of potential interest as magnetic refrigerants for room temperature magnetic refrigeration.

We present an overview of the factors as well as post processing tools allowing optimization of magnetic softness and GMI effect of rapidly quenched materials: microwires and ribbons. Generally, low coercivity and high GMI effect have been observed in as-prepared Co-rich compositions. Annealing at adequate conditions can be very effective for manipulation of the magnetic properties and GMI effect of amorphous and nanocrystalline rapidly quenched materials. After annealing of Co-rich compositions, we can observe transformation of inclined hysteresis loops to rectangular. However, at certain annealing conditions GMI effect can be improved. Using stress-annealing, GMI effect of both Fe-rich and Co-rich microwires as well as of amorphous ribbons can be improved. On the other hand, in Fe-rich FeCuNbSiB microwires after appropriate annealing we observed considerable magnetic softening and GMI effect enhancement. The other promising post-processing allowing GMI effect optimization is Joule heating.

Geometrical, chemical, optical and ionic transport changes associated with ALD of TiO2-coating on the porous structure of two nanoporous alumina membranes (NPAMs), which were obtained by the two-step aluminum anodization method but with different pore size and porosity, are presented. Chemical and morphological changes were determined by analyzing XPS spectra and SEM images, showing practically total coverage of the NPAMs surface and leading to a reduction in the geometrical parameters of both samples, while SAED and high resolution TEM measurements allowed us to determine the crystalline structure and thickness of the TiO2-coating, with the latter confirmed by depth-profile XPS analysis. Spectroscopic ellipsometry measurements were also carried out in order to detect changes in characteristic optical parameters (refractive index, n, and extinction coefficient, k), due to the TiO2-coating of NPAMs. Considering the common application of NPAMs in solute/ion diffusion processes, the effect of the TiO2-coverage on electrochemical parameters was analyzed by measuring the concentration potential with a typical model electrolyte (KCl solutions), leading to an increase of the electropositive character for both kinds of samples.

The magnetic properties of radially oriented Co, Ni, and CoNi alloy nanowires synthesized by pulsed electrodeposition into porous alumina structures are measured and compared with those of similar nanowires grown in a planar geometry. The alloy composition affects the anisotropy axis direction, which is determined by the balance between the magnetocrystalline and shape anisotropies, lying transverse to the nanowires for Co samples and along the nanowire axis for Ni. Monte Carlo simulations were performed to model the magnetic hysteresis of the radially oriented and planar geometry nanowires using an approach based on the conical distribution of anisotropies. The model provides an excellent fit compared with experimental hysteresis loops.

We investigated the effect of the application of dc bias current I-B on the off-diagonal magnetoimpedance (MI) components at 50 MHz in nearly-zero magnetostrictive Co66.5Fe3.5Si12.0B18.0 amorphous ribbons in as-cast and stress-annealed state. The off-diagonal MI component is anti-symmetrical with near-linear behavior within a certain field interval. For the off-diagonal response, the dc bias current is necessary to eliminate transverse domains present in the ribbon. A highly asymmetry of the off-diagonal dependence with the axial magnetic field was obtained when the bias current is applied along the ribbon. A rather high slope at the zero-field point was obtained, being more pronounced in the stress-annealed samples. This is probably related with the domain structure reorganization under the effect of the bias current. This behavior is ideal for a practical sensor circuit design.

This work investigates the effect of self-assembled impurities on magnetic and magnetocaloric properties of the La0.3Ba0.7MnO3 and the La0.3Sr0.7MnO3 compounds. The x-ray diffraction patterns show multiple secondary phases in the as prepared conditions due to the incomplete interaction among reactants. However, the homogeneity is enhanced gradually by increasing the sintering temperature until a high purity phase is obtained at the 1200 degrees C sintering temperature. Results show that the magnetic and the magnetocaloric properties are promoted with the homogeneity and sintering temperature, where there is a monotonic increase in the saturation magnetization and the Curie temperature with the increase of sintering temperature. In addition, the magnetic entropy change of the La0.3Sr0.7MnO3 compound increases from 0.1 J/kgK for the as prepared condition to 0.2 J/kg K and 0.8 J/kg K for the 800 degrees C and the 1200 degrees C sintering temperatures, respectively. And for the La0.3Ba0.7MnO3 compound, the magnetic entropy change shows the values of 0.35 J/kg K and 0.78 J/kg K for the 800 degrees C and 1200 degrees C sintering temperatures respectively.

The giant magnetoimpedance effect (GMI) typically observed in soft magnetic materials has open new opportunities of research owing to the promising and, even nowadays, real technological applications [1].

Design of novel multisegmented magnetic nanowires can pave the way for the next generation of data storage media and logical devices, magnonic crystals, or in magneto-plasmonics, among other energy conversion, recovery, and storage technological applications. In this work, we present a detailed study on the synthesis, morphology, structural, and magnetic properties of Ni, Co, and Ni-Co alloy and multisegmented Ni/Co nanowires modulated in composition, which were grown by template-assisted electrodeposition employing nanoporous anodic aluminum oxide as patterned templates. X-ray diffraction, and scanning and high-resolution transmission electron microscopies allowed for the structural, morphological, and compositional investigations of a few micrometers long and approximately 40 nm in diameter of pure Ni and Co single elements, together with multisegmented Ni/Co and alloyed Ni-Co nanowires. The vibrating sample magnetometry technique enabled us to extract the main characteristic magnetic parameters for these samples, thereby evaluating their different anisotropic magnetic behaviors and discuss them based on their morphological and structural features. These novel functional magnetic nanomaterials can serve as potential candidates for multibit magnetic systems in ultra-high-density magnetic data storage applications.

One-way shape-memory effect (SME) controlled by temperature and magnetic field in rapidly melt-quenched (RMQ) Heusler-alloy (Ni53Mn24Ga23) ribbons is experimentally studied. Two-way SME that results from training is demonstrated for submicron Ni53Mn24Ga23 samples. Reversible thermally and magnetically controlled bending of no less than 1.5% and deflection of no less than 2 μm are reached for composite Ni53Mn24Ga23/Pt microactuators with sizes of 25 × 2.3 × 1.7 μm3 in the presence of magnetic field of μ0 Н = 8 T at an initial temperature of 63°С.

Polycrystalline La0.7Ba0.3MnO3 manganite compound with high homogeneity was prepared by the sol-gel method. This compound shows a metal-semiconductor dc resistivity transition at T-ms temperature of 300 K. The resistivity shows a dc electric field dependence relation, where, it increases monotonically with the applied dc electric current. In contrast, the T-ms is insensitive to the applied electric field, where, it is kept unchanged. The dramatic increase in the dc resistivity with the applied electric current leads to a positive electroresistance that also increases monotonically with the applied electric current. The ac resistivity and the effect of low frequencies are also studied, the results show the monotonic increase in the ac resistivity with increasing the frequency due to the skin effect. The zero frequency (dc) magnetoresistance is enhanced with the frequency increase, where, the magnetoresistance peak shows the values -2.05, -2.9, -4.5 and -4.8% for dc, 3, 70 and 128 Hz, respectively. The dc magnetization measurement shows the ferromagnetic-paramagnetic transition at 300 K revealing the room temperature magnetocaloric properties for the La0.7Ba0.3MnO3 compound. For example, it shows a magnetic entropy change (Delta S) of 1.3 J kg(-1) K-1 with a relative cooling power of 41 J kg(-1) at 2 T applied magnetic field. In addition, the experimental data of Delta S were modeled by Landau theory that proves the absence of elastic, magnetoelastic and magnetoelectronic coupling effects in the magnetocaloric properties. (C) 2016 Elsevier B.V. All rights reserved.

The growth of nanostructured materials by means of different deposition methods employing nanoporous anodic aluminum oxide membranes as patterned templates has been widely used during last years due to the outstanding features displayed by these nanoporous templates. here we report on the synthesis. morphology and magnetic properties exhibited by novel magnetic 1D and 2D nanostructured materials having nanowire or antidot thin films geometry respectively, together to that of geometrically diameter modulated ferromagnetic nanowires. Their magnetic properties will be analyzed and discussed based on the different anisotropic behavior derived from their morphological and microstructural features.

In this study, we investigate structural, magnetic, magnetocaloric and thermoelectric properties of La0.7Sr0.3Mn1-xNixO3 compounds with 0.025 <= x <= 0.125. X-ray diffraction analysis shows the structure transformation from the R-3c rhombohedral to the Pbnm orthorhombic structure with Ni2+ doping at x >= 0.075 composites. The dc thermal magnetization measurements reveal the monotonic decrease in both Curie temperature and magnetization values with Ni2+ addition. The change in magnetic properties of the studied system is correlated to the ferromagnetism suppression and the antiferromagnetism promotion according to some cooperative intrinsic and extrinsic factors. Results show that Ni2+ addition affects the magnetocaloric properties, where it shifts the maximum value of the magnetic entropy change towards lower temperatures with relative cooling power of 88, 105, 47 J/kg for x = 0.025, 0.075 and 0.125 composites, respectively. Moreover, it is observed that Ni2+ doping increases the absolute value of Seebeck coefficient and decreases hole conduction interval. (C) 2016 Elsevier B.V. All rights reserved.

We report on fabrication, structural and magnetic properties of novel Hensler-type glass coated Ni2FeSi microwires that were prepared by the Taylor-Ulitovsky method, having a metallic nucleus diameter about 3.9 mu m and total sample diameter of 39 mu m. This single step and low cost fabrication technique offers to prepare up to km of glass-coated microwires starting from few g of cheap elements for diverse applications. The X-ray diffraction data from the metallic nucleus indicates L2(1) crystalline structure (a = 5.563 (A) over circle), with a possible DO3 disorder. Magnetic measurements determined the Curie temperature well above the room temperature (770 K) together with uniform easy magnetization axis of the metallic core, which predisposes this material to a suitable candidate for spintronic applications.

Changes associated to surface functionalization of nanoporous alumina membranes by atomic layer deposition (ALD) of metal oxides (Al2O3, SiO2, TiO2, Fe2O3, ZnO) are presented. ALD modification of the alumina membranes reveals a reduction up to 25-35% in porosity, and confirms the presence of the metal oxide layer coating the pores. Its effect on the membrane permselectivity and other characteristic transport parameters was determined from membrane potential measurements, being correlated with changes in morphology and physic-chemical characteristics of the alumina membranes. According to our results, ALD provides a straight-forward and efficient method to adjust membrane performance for specific applications. (C) 2017 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved.