Thermal, structural and magnetic characterization of Co-based alloys (original) (raw)
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Magnetic properties of Co-based amorphous ribbon under cyclic heating and cooling
ISSUES, 2010
Purpose: The aim of the work is to investigate the changes of magnetic properties of the cobalt based Co68Fe4Mo1Si13.5B13.5 alloy under cycling heating and cooling. Design/methodology/approach: The amorphous metallic ribbons were manufactured by planar-flow-casting method. Investigations of the magnetic properties were observed under permanent heating amorphous and partially crystallized alloy. Observations of the structure were made on the JOEL transmission electron microscope (TEM). Using the HFQS program the distributions of the magnetic hyperfine P(H) fields were determined for spectra smoothed in this way, employing the Hesse-Rübartsch method. Findings: The analysis of the magnetic properties under permanent heating and structure of the Co-based amorphous ribbons obtained in the by planar-flow-casting process proved that the permanent heating caused the crystallization of second magnetic phase after transition near to paramagnetic state. Research limitations/implications: The appropriate cyclic heating and cooling significantly decreasing soft magnetic properties of examined amorphous alloy. The cyclic heating beginning of elementary crystallization processes and the end of crystallization alloy. Practical implications: According to the results presented in the paper the examined Co-based glassy alloys as a soft ferromagnetic material may be utilized in construction of magnetic cores such as choke coils, common mode and noise filter and is of great technological interest. Originality/value: The paper presents influence of permanent heating on structural changes of metallic ribbons. Results and discussion of the influence of permanent heating on magnetic properties of metallic ribbon are presented.
Anisotropic Mechanical and Giant Magneto-Impedance Properties of Cobalt-Rich Amorphous Ribbons
Journal of Electronic Materials, 2016
A comparative study was performed on the mechanical and giant magnetoimpedance (GMI) properties in the longitudinal and transverse directions of Co 69 Fe 4 Ni 1 Mo 2 B 12 Si 12 amorphous ribbons. Both mechanical and GMI properties were found to be anisotropic. Kerr microscopy shows the presence of a stripe-type domain structure with the magnetic easy axis parallel to the longitudinal direction. The fracture strength, elastic modulus, and fracture toughness in the transverse direction was higher than those in the longitudinal direction. A larger GMI response was achieved in the transverse direction at a frequency range where both the domain wall motion and spin rotation dominantly contributed to the effective permeability and hence the magnetoimpedance. The current study paves the way for designing Co-rich amorphous ribbons as desirable components in electronics such as magnetic sensors.
COMPORTAMIENTO MAGNÉTICO Y EFECTO DE MAGNETO-IMPEDANCIA EN CINTAS DE CoFeBSi
2012
In this paper we present dc magnetization, ac susceptibility and impedance measurements on amorphous alloy ribbons Co 80-x Fe x B 10 Si 10 with x = 0, 6, 8 and 10 at.%. They indicate that at room temperature these samples have good soft magnetic behavior including the giant magneto-impedance effect. The real part of the ac susceptibility χ’ ac reveals an irreversibility field, H irr , which corresponds to the transverse anisotropy field, H k , at which the magneto-impedance ratio reaches its maximum value.
przyrbwn.icm.edu.pl
The object of this work is the comparison of domain structure and off-diagonal magnetoimpedance effect in amorphous ribbons with different magnetostriction coefficient. The Co 66 Fe 4 Ni 1 Si 15 B 14 and Fe 80 B 20 samples were obtained by melt-spinning. During the quenching procedure a 0.07 T transverse magnetic field was applied to some of the samples. Domain patterns obtained by the Bitter technique confirm that the differences on the samples are related to the different anisotropy and magnetostriction coefficient, and the quenching procedure. Small changes on the anisotropy distribution and the magnetostriction coefficient can be detected by the off-diagonal impedance spectra as a consequence of the different permeability values of the samples.
Study of Giant Magneto-Impedance Behavior in Co–Fe Based Amorphous/Nanocrystalline Materials
Materials and Manufacturing Processes, 2006
Giant magneto-impedance (GMI) behavior have been studied in melt spun Co 71−X Fe X Cr 7 Si 8 B 14 (X = 0 2 3 2 4 6 8, and 12 at%) alloys. The addition of Fe in the system changed the saturation magnetostriction constant from negative to positive values. The GMI property was measured with a driving current of 5 mA and 4 MHz frequency using a spectrum analyzer. The GMI ratio increased with the increase of the applied dc field and became maximum at a field H k known as the anisotropy field of the materials. The maximum of GMI ratio (GMI max) depended on the Fe content and was maximum (12%) for Fe = 4 at% for the alloys in the as-melt spun state. Substantial increase of GMI max to 66% for Fe = 4 at% was observed after annealing the sample at 673 K.
AC magnetic and magnetoimpedance properties of CoFe(NbMnNi)BSi amorphous ribbons
Journal of Magnetism and Magnetic Materials, 2018
We report magnetic and magnetoimpedance (MI) properties of cobalt-rich amorphous alloys to investigate the role of small quantities of 3d or 4d transition-metal elements in Co-rich alloys. The microstructure, thermal stability, AC soft magnetic properties and magnetoimpedance of the ribbons are investigated by substituting Nb in place of Ni and Mn. Present study shows an improvement in glass forming ability and reduction in electrical conductivity of the ribbon with Nb substitution. Higher Nb containing alloy shows minimum core loss compared to other compositions over a range of frequencies. Ribbon with higher core loss exhibited higher MI ratio (~100% at 3 MHz), but decreased rapidly at higher frequencies due to its larger electrical conductivity. The ribbon with lower electrical conductivity showed a steady MI ratio and field sensitivity with frequency. These results indicate that MI and core losses at medium range of frequencies can be tuned by adding Nb that provides most favourable electrical conductivity and magnetic permeability values, which result in optimum skin depth and MI. The effect of electrical conductivity on MI is also validated through numerical simulations using standard electrodynamics models.
Soft Magnetic Properties of Co-Based Amorphous Alloy by Two-Step Cooling Method
physica status solidi (a), 2002
The soft magnetic properties of Co-based amorphous Co 66 Fe 4 Ni 1 Si 15 B 14 alloy in terms of various annealing conditions have been investigated by magnetoimpedance (MI) effect and permeability ratio (PR). In order to enhance the soft magnetic properties by co-reducing internal thermal stress and magnetic ordering, we applied the furnace cooling to Curie temperature and subsequent water quenching (F&W) method, which considerably increased the initial permeability -to values 60% or 100% higher than in the only furnace-cooled (FC) or water-quenched samples, respectively. However, the MI and PR results show that the FC sample is softer than the F&W sample at high frequencies.
Magnetic properties of amorphous Co$_x$Nb$_{100-x}$ alloys produced by mechanical alloying
2004
Three amorphous Co$_x$Nb$_{100-x}$ alloys, Co$_{25}$Nb$_{75}$, Co$_{57}$Nb$_{43}$ and Co$_{80}$Nb$_{20}$, were produced by Mechanical Alloying starting from the elemental powders. Their magnetic properties were determined using an alternating gradient force magnetometer (AGFM), and the remanent magnetizations, saturation fields and coercive fields were obtained from the hysteresis loop. The alloys have a relatively high saturation field, which decreases as the composition becomes richer in Co. The coercivity and remanent magnetization reach an optimal value around 57% at.Co, making {\em a}-Co$_{57}$Nb$_{43}$ the hardest magnetic material among the three alloys. Further addition of Co produces a soft alloy.
Magneto-Impedance behavior of Co-Fe-Nb-Si-B-based ribbons
Journal of Magnetism and Magnetic Materials, 2010
The giant magneto-impedance of melt spun Co x Fe 72 À x Nb 4 Si 4 B 20 (x =10, 20, 36, 50) amorphous and nanostructured ribbons have been investigated. Alloys have been optimized at the driving current amplitude, frequency and found that amorphous ribbon of nominal composition of Co 36 Fe 36 Nb 4 Si 4 B 20 shown maximum GMI ratio of 13%. The behaviour of the driving current amplitude on the GMI behaviour was studied and the sample was optimized for driving current amplitude, I ac =10 mA. The frequency dependence of the GMI behaviour was studied for the ribbon sample Co 36 Fe 36 Nb 4 Si 4 B 20 at frequency in the range of 100 kHz-1.2 MHz of the optimized driving current amplitude and it was found that the sample showed the maximum GMI behaviour at f= 700 kHz. The optimized samples were Joule heated at the current density J= 0-35 A/m 2 for a period of 1 min. The GMI ratio initially increased then progressively deteriorated with J, but after a certain range it shows up to 16% of improvement in the magneto-impedance value due the increase of nanocrystalline volume fraction. The asymmetry in the GMI profile was observed for the sample Joule heated at J= 1-5 A/m 2 for 1 min.