Nonmagnetic Alloys Research Articles

Fabrication and magnetic study of Co/Pt multilayer nanowires and Co–Pt alloy nanowires electrodeposited into porous Si substrates

In this work, we grow composite structures consisting of magnetic and non-magnetic metal or alloy nanowires electrodeposited into the ion etched tracks previously created inside Si substrates. The holes are then filled by Co–Pt alloys and Co/Pt multilayers using electrodeposition technique making a large number of parallel nanowires. This process takes place in a single electrolyte containing Co+2 and Pt+4 ions by applying a proper deposition potential using a computer control potentiostat. The magnetic properties of the sample were studied using vibrating sample magnetometer. Magnetoresistive behaviour of the nanowire samples was then studied by subjecting the samples to an external magnetic field. The results show that the Co/Pt multilayered nanowires exhibit a large magnetoresistance, while the Co–Pt alloys only show anisotropic magnetoresistance. This result could be of a great interest for the sensor fabrication community as they will provide a view on a very important direction of the development of the wide spread sensor industry, and more importantly for understanding the physical phenomena underlying the magnetic/non-magnetic nanostructures.

Fe-Mn-Si/6.5wt%Si-Fe Bilayer Ribbons produced by Using Melt Spinning Technique

Recently, progress of the intelligent materials plays a big role in development of science and technology. We have ever tried to develop ferromagnetic shape memory alloys to expand application range of the common non-magnetic shape memory alloys, which are typical intelligent material. However the saturation magnetization and the shape memory effect were in a relation of trade-off, so we couldn’t get a good result. In this research, we tried to develop ferromagnetic shape-memory alloys as a composite material by using the single-roll melt spinning technique. They are bilayer ribbons, which have both shape memory layer and magnetic layer.

Mössbauer Study of Annealed Fe/Sn Multilayer

[Fe(35 A)/Sn(45 A)]60 multilayer film have been prepared by a vacuum evaporation method, followed by an annealing treatment in vacuum at different temperatures going until 641 K for 3 h. This multilayer has been studied by 57Fe Mossbauer spectrometry at room temperature; it shows that we have formation of defined compound FeSn with thickness 11 A at the interface between the temperatures 588 and 641 K. For the temperature below 598 K, we noticed an increase in the proportion and composition of the nonmagnetic amorphous alloy when the annealing temperature increases. Mossbauer spectroscopy also shows that the Fe in the multilayer is in a α-Fe state.

Thermal and Electrical Transport Properties of Zr-Based Bulk Metallic Glassy Alloys with High Glass-Forming Ability

Thermal and electrical transport properties, such as thermal diffusivity, the electrical resistivity and thermopower of the Zr-based bulk metallic glassy (BMG) alloys of Zr42Cu42Ag8Al8 and Zr55Al10Cu35−xNix (x = 0, 5 and 10) with high glass-forming ability were investigated. Thermal diffusivity is comparatively low at about 2 × 10−6 m2 s−1, reflecting the aperiodic crystal structure of the BMG, whereas it becomes higher and depends on the alloy compositions after their crystallization. The phonon contribution to the thermal conductivity of the BMG alloys is thought to be small, based on a comparison with the estimated value of the electronic contribution to the thermal conductivity from the Wiedemann–Franz law. The thermopower of the present Zr-based BMG alloys shows a small positive value around room temperature, which is a general feature of nonmagnetic amorphous alloys.

SANDVIK BIOLINE F562/F562L TI

Abstract Sandvik Bioline F562/F562L Ti are nonmagnetic nickel-cobalt base alloys with ultra high strength and great corrosion resistance. This datasheet provides information on composition, physical properties, hardness, elasticity, and tensile properties. It also includes information on forming. Filing Code: Ni-693. Producer or source: Sandvik Steel Company.

Acoustic emission in martensitic transformations

Acoustic emission originates during martensitic transformations from sudden local changes of the displacement field across the propagating interfaces. Acoustic emission reveals the jerky character of the dissipation of the elastic energy excess, which proves that the transition occurs through avalanches. In this paper we show that the analysis of acoustic emission within an appropriate framework is a very useful technique, which provides quantitative dynamical information complementary to that obtained from more standard techniques. In particular, we will show that the probability density function of amplitudes, energies and durations of the detected acoustic signals follows power-law distributions related to avalanche criticality. This is illustrated with examples for non-magnetic and magnetic shape-memory alloys under selected external conditions.

Measurement of electrical conductivity of copper under impulsive loading

A noncontact method of measurement of electrical conductivity of nonmagnetic metals and alloys under impulsive loading is proposed. It is based on experimental determination of the nature of decay of eddy currents in the studied sample, which is a finite size foil disk. Theoretical justification of the proposed method is given. Experiments on determination of copper conductivity at pressures up to 16 GPa are performed.

Fe–Mn–Si/6.5wt%Si–Fe Bilayer Ribbons Produced by Using the Melt-Spinning Technique

Recently, progress of the intelligent materials plays a big role in development of science and technology. We have ever tried to develop ferromagnetic shape-memory alloys to expand the application range of the common nonmagnetic shape-memory alloys, which are typical intelligent material. However the saturation magnetization and the shape-memory effect were in a relation of the trade-off, so we could not get a good result. In this study, we tried to develop ferromagnetic shape-memory alloys as a composite material by using the single-roll melt-spinning technique. They are bilayer ribbons, which have both shape-memory layer and magnetic layer.

Extrinsic Spin Hall Effect Induced by Iridium Impurities in Copper

We study the extrinsic spin Hall effect induced by Ir impurities in Cu by injecting a pure spin current into a CuIr wire from a lateral spin valve structure. While no spin Hall effect is observed without Ir impurity, the spin Hall resistivity of CuIr increases linearly with the impurity concentration. The spin Hall angle of CuIr, (2.1±0.6)% throughout the concentration range between 1% and 12%, is practically independent of temperature. These results represent a clear example of predominant skew scattering extrinsic contribution to the spin Hall effect in a nonmagnetic alloy.

Half-metallic Fe2CrSi and non-magnetic Cu2CrAl Heusler alloys for current-perpendicular-to-plane giant magneto-resistance: First principle and experimental study

We present results of our first principle and experimental study on new Heusler alloys candidates for half-metallic electrode and nonmagnetic spacer in current-perpendicular-to-plane giant magneto-resistance devices. The electronic structures of Fe2CrSi and Cu2CrAl are characterized by high density of states at the Fermi level in the majority spin band with a good match in their majority band structures near the Fermi level. The calculated interfacial spin polarization in Fe2CrSi/Cu2CrAl (100) superlattice is ∼80%. We have also epitaxially grown ferromagnetic A2 Fe-Cr-Si and nonmagnetic L21 Cu-Cr-Al (100) films on Cr-buffered MgO(100) substrates.

Electronic band structure matching for half- and full-Heusler alloys

We explore the lattice and the electronic band structures matching between the half-metallic Heusler alloys (half-Heusler NiMnSb and full-Heusler Co 2MnSi) and several hypothetical non-magnetic Heusler alloys by using first principle calculations. The lattice and band structure matching are almost perfectly satisfied between the two materials of similar crystal structures: (i) NiMnSb and XYSb and (ii) Co 2MnSi and X 2YSi, where X, Y=Ni or Cu. Owing to the high interface spin scattering asymmetry, these materials are promising to realize a high giant magnetoresistance at room temperature.

Electrodeposition and Characterization of CoO/ZnO Composite Dendritic Structures Consisted of Hexagonal Nanoplatelets

Ferromagnetic–nonmagnetic heterogeneous alloy nanostructures are attracting growing interest because of their special physical properties, such as giant magnetoresistance effect and mixed magnetism produced by the change in structure, magnetism, or electrical transport. Here, we report a synthesis route for the preparation of CoO/ZnO alloy dendritelike structures consisting of orderly organized hexagonal nanoplatelets by electrochemical deposition in a solution of at . The main trunk and side branches of the CoO/ZnO alloy dendritelike structure are regularly angled, and each branch is made of periodic hexagonal nanoplatelets. The effects of electrodeposition parameters on the compositions of CoO/ZnO alloy dendritelike structures were studied. The morphologies of CoO/ZnO alloy dendritelike structures can be well controlled by changing deposition current densities or the concentration of . The formation process of the dendritelike arrangement of periodic CoO/ZnO alloy hexagonal nanoplatelets was investigated in this paper. A magnetization measurement indicates that these prepared CoO/ZnO alloy dendritelike structures have a soft ferromagnetic behavior at 120 K and a vortex magnetization at 215 K.

Method for determining the electrical conductivity of nonmagnetic metals under dynamic loading

A noncontact method for determining the electrical conductivity of nonmagnetic metals and alloys under shock-wave loading was developed. The method is based on recording the eddy-current decay rate in a foil of the material studied. The conductivity of aluminum was measured at pressure up to 14 GPa.

Effect of the austenite stability on the fracture mode and mechanical properties of aging nonmagnetic alloys after different strengthening treatments

Aging austenitic alloys with a stable (N26Kh5T3; Ms < −196°C) and metastable (N25Kh2T3; Ms = −130°C) austenite have been investigated after employing different methods of heat and thermomechanical treatments, namely, (1) aging at a temperature Ta = 600°C (A); (2) strengthening using phase-transformation-induced hardening (“phase naklep” (PN)) and subsequent aging at Ta = 600°C (PN + A); (3) deformation to 30% (D) at Td = 600°C after preliminary aging at the same temperature (A + D); and (4) PN + A + D. In this case, the alloy with stable austenite has not been strengthened by phase naklep. Structure, fracture mode, ultimate strength, yield strength, relative reduction of area, and relative elongation have been studied depending on the duration of aging τa upon these strengthening treatments. It has been established that the physicomechanical properties of the alloys depend not only on τa, but also on the testing temperature. It is shown that all above physicomechanical characteristics of the alloys under consideration are affected substantially by the austenite stability.

Metal artifacts in MRI from non-magnetic dental alloy and its FEM analysis

Artifacts in MR(Magnetic Resonance) images of oral cavity produced from non-magnetic metal restorations was verified by measuring the image of index finger and a cylinder of fat test piece with a type 4 gold alloy ring using a compact MRI equipment. In the images of finger, portion around the ring disappeared. However, it was nearly restored with a cut ring. In the cylinder of fat test piece, obvious artifacts appeared when circumferential surface of the ring was placed perpendicular to RF(Radio Frequency) field of MRI equipment's excitation/detection coil. However, in other directions or with a cut ring, artifact disappeared. The cause was simulated with FEM(Finite Element Method) electromagnetic field analysis, and alternating magnetic field was shown to induce surface current on the continuous gold ring. Magnetic field produced by that current interfered with the field from excitation coil. This demonstrated the characteristics and cause of artifacts by non-magnetic dental metals.

A bistable magnetically enhanced shape memory microactuator with high blocking forces

A novel approach of combining nonmagnetic shape memory alloy (SMA) microactuators with electroplated magnetic layers (ML) is presented, which enables the use of two intrinsic actuation principles in a single SMA-ML component allowing considerable gain in functionality. In the present work, we demonstrate local electroplating of Ni-81.75at.%Fe discs onto the surface of Ti-49at.%Ni microbridge structures. Antagonistic SMA-ML microactuators are fabricated by mechanically coupling two SMA-ML microbridges in their center by a spacer and prestraining them with respect to each other. The SMA-ML microactuators show bistable performance in the presence of an inhomogenous magnetic field generated by permanent magnets near the magnetic discs. Compared to antagonistic SMA microactuators fabricated without electroplated discs, a considerable improvement of mechanical performance is achieved. Magnetically enhanced SMA-ML microactuators of 7×7×4mm3 overall size show a blocking force and bistable stroke of about 33 mN and 84μm, respectively, while corresponding conventional SMA microactuators show no blocking force and a considerably smaller bistable stroke of 15μm.

The band structure-matched and highly spin-polarized Co2CrZ/Cu2CrAl Heusler alloys interface

Here we present a lattice- and band-matched nonmagnetic L21 Heusler alloy spacer for Co2CrZ Heusler alloys where Z=Si or Al. By first principle calculations, we find that the band structure matching is almost perfectly satisfied when they are interfaced with Cu2CrAl. Despite the loss of half-metallicity due to interface states, our calculations show that the spin polarization at these band-matched (001) interfaces is higher than 80%. These lattice-matched Co2CrZ/Cu2CrAl interfaces with excellent band matching and enhanced spin scattering asymmetry are promising for all-metallic current-perpendicular-to-plane giant magnetoresistance device applications.

Transmission measurements of guides for ultra-cold neutrons using UCN capture activation analysis of vanadium

The efficient transport of ultra-cold neutrons (UCN) from their source to the experimental site is a major issue for various kinds of precision experiments. Neutron guides often have to transport the UCN several tens of meters with acceptable losses. In order to qualify the guides, their UCN transmission properties have to be determined with high precision. For this purpose we have developed a novel method. The transmitted UCN were absorbed at the end of the guide in a vanadium disc producing the β-emitter 52 V (half life 3.74 min). The intensity of the 1434 keV γ-ray following the β-decay was measured. UCN guides of non-magnetic nickel alloys made by the replication technique were studied. They show a high Fermi pseudopotential V F for UCN and a low surface roughness. For these guides the transmission per meter was determined with a relative error of ±0.6%, resulting in values above 0.95/m. By an absolute calibration of the γ-ray detection system we also deduced the absolute value of the UCN current absorbed in the vanadium plate. Possible applications of this method are discussed.

Influence of Nickel layer thickness on the magnetic properties and contact resistance of AuGe/Ni/Au Ohmic contacts to GaAs/AlGaAs heterostructures

The magnetization of alloyed Ohmic contact film structures of the form AuGe/Ni/Au deposited on a GaAs/AlGaAs heterostructure substrate are reported as functions of Ni-layer thickness and alloying temperature. The observations are correlated with contact resistance and surface morphology studies. It is found that drops in magnetization, due to conversion of Ni to a non-magnetic phase or alloy, begin at anneal temperatures as low as 100 °C for all Ni-layer thicknesses. The conversion is completed at an anneal temperature, TA, that increases with Ni-layer thickness. TA varies from 100–200 °C to 400–430 °C as Ni-layer thickness is varied from 10 to 100 nm for an AuGe (88 : 12 wt%) layer thickness of 100 nm. The electrical contact formation, however, appears to begin at much higher temperatures than 100 °C. Lowest contact resistance (0.05 ± 0.01 Ω mm) is obtained when Ni thickness is about 25 nm for 100 nm AuGe layer thickness, anneal temperature is 400 °C and anneal duration is 60 s. This contact is non-magnetic. Measurements on samples with other AuGe layer thicknesses suggest that the contact resistances are comparable to this optimum value, if the ratio of AuGe layer thickness to that of Ni is ⩾4. Increasing the Ni-layer thickness reduces the roughness of annealed contacts, but also increases contact resistance. The magnetic measurements are suggestive of a transformed Ni-layer thickness proportional to the thickness of the underlying AuGe layer. It is proposed that Ni diffuses into AuGe in a concentration limited diffusive mechanism followed by segregation into Ni3Ge.

Kinetics of alloy formation at the interfaces in a Ni-Ti multilayer: X-ray and neutron reflectometry study

Vacuum-deposited Ni/Ti multilayers on annealing at different temperatures exhibit formation of ordered alloy layers at interfaces. We have studied in detail the formation of alloy at interfaces of a Ni/Ti multilayer on annealing at $300\text{ }\ifmmode^\circ\else\textdegree\fi{}\text{C}$ and $400\text{ }\ifmmode^\circ\else\textdegree\fi{}\text{C}$ using powder x-ray diffraction, x-ray reflectometry, polarized neutron reflectometry, and off-specular x-ray reflectometry techniques. Correlation among structural, magnetic, and morphological properties in as-deposited Ni/Ti multilayer as well as in a sample annealed at $300\text{ }\ifmmode^\circ\else\textdegree\fi{}\text{C}$ and $400\text{ }\ifmmode^\circ\else\textdegree\fi{}\text{C}$ has been studied. X-ray diffraction technique was used to obtain crystal structure of the sample. Specular x-ray reflectometry and neutron reflectometry were used to determine the growth of alloy layers from density profile, as a function of depth in the sample. From off-specular x-ray reflectivity we found that the in-plane correlation lengths at the interfaces grew with annealing. This is associated with alloy crystallite growth obtained from x-ray reflectometry. Detailed magnetic-moment density profile of as-deposited as well as annealed multilayer sample has been determined by polarized neutron reflectometry measurements, which was used to determine the magnetic nature of the alloy layers. The results show formation of nonmagnetic alloy layers at the interfaces on annealing. From the Bragg-peak intensities of x-ray reflectivity and polarized neutron reflectivity measurements, we have estimated the diffusion lengths after annealing at $300\text{ }\ifmmode^\circ\else\textdegree\fi{}\text{C}$ and $400\text{ }\ifmmode^\circ\else\textdegree\fi{}\text{C}$.