S. Atalay

Amorphous wires and their applications

Abstract The basic physical and magnetic properties of Fe and Co based amorphous wires are summarised, together with post-production treatments used to modify the properties of the as-quenched alloys. The current status of the core-shell domain model is reviewed in the light of recent studies of the internal stress and easy axis distributions. Finally, a survey of recently proposed applications is presented.

Magnetostrictive and magnetoelastic properties of rapidly quenched wire

The magnetostrictive and magnetoelastic properties of amorphous wires produced by rapid quenching in rotating water are reviewed, with particular reference to the domain structure. Saturation magnetostriction and engineering magnetostriction of as-quenched and annealed wires having compositions of the type Fe/sub x/Co/sub 1-x/Si/sub y/B/sub 15/ (y=7.5-15) are discussed. The magnetoelastic properties reviewed are the field-dependent Youngs modulus and shear modulus (/spl Delta/E and /spl Delta/G effects) and magnetomechanical damping (internal friction). >

Magnetoimpedance effect in electroplated NiFeRu/Cu wire

Magnetoimpedance (MI) and hysteresis loops were studied in electroplated Ni79.1Fe20.9/Cu, Ni75.64Fe24.26Ru0.10/Cu, Ni79.51Fe20.31Ru0.18/Cu and Ni75.99Fe23.66Ru0.34/Cu wires. Scanning electron micrographs showed that crack-free electroplated wires were obtained with a smooth surface. The average grain size varied between 3 and 10 µm for all samples. It was found that circumferential anisotropy was induced in all samples during the electroplating process. The maximum MI response was 459% at a frequency of 90 kHz, 361% at 110 kHz, 157% at 100 kHz and 114% at 340 kHz for Ni79.1Fe20.9/Cu, Ni75.64Fe24.26Ru0.10/Cu, Ni79.51Fe20.31Ru0.18/Cu and Ni75.99Fe23.66Ru0.34/Cu wires, respectively.

Electrical Transport and Magnetoresistance of La 0.67 Ca 0.33 MnO 3 : Ag x (x = 0, 0.1, 0.2, 0.3, 0.4) Composites

The structural, magnetic and magnetotransport properties of La 0.67 Ca 0.33 MnO 3 : Agx (x = 0, 0.1, 0.2, 0.3 and 0.4) composites were investigated systematically. X-ray and EDX analysis indicated that Ag is not substituted into the main La 0.67 Ca 0.33 MnO 3 phase and remains an additive to the second phase at the grain boundary. The Curie temperature first decreased from 269 K for x = 0 to 257 K for x = 0.1 and then remained nearly unchanged with increasing Ag content. For the x > 0.1 samples, a second transition temperature (T MI2 ) was observed in the resistance curves. At temperatures below 150 K, a significant enhancement in MR was observed while high temperature MR decreased with increasing Ag content. The maximum MR was observed to be 55% in the x = 0.4 sample at 10 K and a 6T magnetic field, this value is larger than that of pure La 0.67 Ca 0.33 MnO 3 (53% at 265 K and 6 T). In addition, at low fields (H < 1T), a sharp increase in the MR was observed.

The effect of furnace annealing and surface crystallization on the anisotropy, ΔE and magnetoimpedance effects in Fe71Cr7Si9B13 amorphous wires

The dependence of the magnetization loops, coercivity, anisotropy constant, ?E and magnetoimpedance (MI) effects in positively magnetostrictive Fe71Cr7Si9B13 amorphous wires on annealing conditions were studied. Samples were annealed at temperatures of 440?C and 460?C for durations between 0.3 and 300?min. The results indicate that progressive annealing first leads to relief of internal stresses and annealing of wires at 460?C for 60?min produces the minimum coercivity of about 1?A?m?1. Further annealing increases the coercivity and anisotropy, due to partial crystallization at the surface. It was found that the anisotropy changes its direction to the circumferential direction with the surface crystallization. The maximum change in Youngs modulus was measured to be about 75% in a partly surface crystalline sample. It was observed that the magnitude of the MI effect of the stress relieved sample could exceed 200% at 1?MHz.

ELECTRICAL TRANSPORT AND MAGNETORESISTANCE PROPERTIES OF La0.67Ca0.33MnO3 FILM COATED ON PYREX GLASS SUBSTRATE

The electrical transport and magnetoresistance properties of the polycrystalline La0.67Ca0.33MnO3 film produced on a Pyrex substrate were investigated for the first time. X-ray powder diffraction indicated that the film sample has a perovskite structure. Scanning electron microscope indicated that La0.67Ca0.33MnO3 film thickness is approximately 500 nm, and the average grain size of this sample varies between 40 and 50 nm. La0.67Ca0.33MnO3 film showed a phase transition from paramagnetic to ferromagnetic at (TC) 80 K and a metal–insulator transition at (TMI) 77.5 K and at 2 mT magnetic field. The upturn of the resistance observed at low temperatures (<36 K) was attributed to the Coulomb blockade, and the strong structural disorder is due to the large lattice mismatch and strain relaxation. A large magnetoresistance ratio [MR (%)] of 780% was observed at 100 K and 6 T magnetic field.

Nanowires of lead-free solder alloy SnCuAg

Ternary Sn88Ag5Cu7, Sn93Ag4Cu3, Sn58Ag18Cu24, Sn78Ag16Cu6, Sn90Ag4Cu6, Sn87Ag4Cu9 alloy nanowires were produced at various values of deposition potential by dc electrodeposition on highly ordered porous anodic alumina oxide (AAO) templates. During the deposition process some parameters, such as ion content, deposition time, pH, and temperature of the solution, were kept constant. The diameter and length of regular Sn93Ag4Cu3 nanowires electrodeposited at - 1V were determined by scanning electron microscopy (SEM) to be approximately 200-250nm and 7-8 µm, respectively. Differential scanning calorimetry (DSC) results indicate that the melting onset temperature of Sn93Ag4Cu3 nanowires is about 204°C.

An alternative measurement method for magneto-impedance effect in amorphous alloys

An alternative measurement method for giant magneto-impedance (GMI) effect is described. The method measures pulse width instead of induced voltage between the ends of wire as a function of external applied field. In the measurement method two ac signals are applied to the wire and it has been shown that by changing the amplitude of the low-frequency ac signal a large variation in the field dependence of pulse width can be obtained.

Effect of tensile stress on magnetoimpedance properties of CoNiFe/Cu wire

AC o 20.5Ni40.5Fe39 magnetic film was electrodeposited onto a copper wire 50 µm in diameter. The magnetoimpedance (MI) effect, (�Z/Z) H(%) = ((Z(H ) − Zmax)/Zmax) × 100, was measured in the Co20.5Ni40.5Fe39/Cu composite wire under varying tensile stresses up to 30 MPa. The results showed that large MI and stress impedance (SI) effects can be observed in the Co20.5Ni40.5Fe39/Cu composite wire. The MI curve at zero tensile stress shows a small split peak in the low-field region. With increasing applied tensile stress, single-peak behaviour of the MI effect is observed. The magnitude of the MI and SI effects decreases with increasing tensile stress, σ . The peak values of (�Z/Z) H(%) for the sample decrease from 265% at σ = 0 to 39% at σ = 30 MPa at 40 kHz ac driving-current frequency. The impedance of a sample under the effect of 25 MPa tensile stress at 40 kHz ac driving-current frequency showed variations of about 146%. It was also found that the frequency value, f ∗ , where the maximum MI effect was observed as a function of driving-current frequency, increases with increasing tensile stress.

INFRARED, STRUCTURAL AND MAGNETIC PROPERTIES OF La0.67Ca0.33MnO3 COMPOUND

La0.67Ca0.33MnO3 samples prepared by polymeric precursor route method are investigated using the thermogravimetric, differential thermal analysis, X-ray powder diffraction, scanning electron microscope, infrared spectroscopy and magnetic measurements. The unit cell parameters and grain size for all the samples are refined using X-ray diffraction and scanning electron microscope. It is observed that the IR bands at about 400 cm-1 is are most likely due to Mn–O–Mn bending mode and the band at 600 cm-1 is the result of the in plane Mn–O stretching mode. Magnetization measurements indicated that the Curie temperature increases from 241.3 K for the sample sintered at 600°C to 268.86 K for the sample sintered at 1000°C as a function of sintering temperature. The magnetic entropy change reaches the maximum value of about 4.8J/kg·K for the sample sintered at 1150°C at an applied field of 1 T.