Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userAnisotropic Dependence of Giant Magneto-Impedance of Amorphous Ferromagnetic Ribbon on Biasing Field
46
0
0.0
(
0
)
Added by
Bhaskar Kaviraj Mr.
Publication date
2006
fields
Physics
and research's language is
English
Ask ChatGPT about the research
No Arabic abstract
The magneto-impedance (MI) in amorphous ribbon of nominal composition Fe73.5Nb3Cu1Si13.5B9 has been measured at 1MHz and at room temperature for different configurations of exciting a.c and biasing d.c. fields. A large drop in both resistance and reactance is observed as a function of d.c magnetic field. When the d.c and a.c fields are parallel but normal to the axis of ribbon, smaller magnetic field is needed to reduce the impedance to its small saturated value compared to the situation when fields are along the axis of ribbon. Larger d.c. field is required to lower the impedance when the d.c field acts perpendicular to the plane of the ribbon. Such anisotropy in magneto-impedance is related to the anisotropic response of the magnetization of ribbon. The large change of impedance is attributed to large variation of a.c permeability on the direction and magnitude of the dc biasing field.
rate research
Read More
Magneto-impedance (MI) effects have been observed for amorphous Fe73.5Nb3Cu1Si13.5B9 ribbon which has been excited by an a.c. magnetic field parallel to the length of the ribbon. Maximum relative change in MI as large as -99% was observed which has never been reported before. The relative change in MI, when plotted against scaled field was found to be nearly frequency independent. A phenomenological formula for magneto-impedance, Z(H), in a ferromagnetic material, is proposed based on Pade approximant to describe the scaled behavior of MI.
A two-core transducer assembly using a Fe73.5Nb3Cu1Si13.5B9 ribbon to detect a change of magnetic field is proposed and tested for displacement (linear and angular) and current sensor. Two identical inductors, with the ribbon as core, are a part of two series resonance network, and are in high impedance state when excited by a small a.c field of 1MHz in absence of d.c biasing field (Hdc). When the magnetic state of one inductor is altered by biasing field, produced by a bar magnet or current carrying coil, an ac signal proportional to Hdc is generated by transducer. The results for the sensitivity and linearity with displacement (linear and angular) of a magnet and with field from the current carrying coil are presented for two particular configurations of the transducer. High sensitivities of voltage response as much as 12micro-volt/micro-meter and 3mV/degree have been obtained for the transducer as a linear and angular displacement sensor respectively in the transverse configuration of exciting a.c and biasing d.c fields.
The resistive and reactive parts of the magneto-impedance of sintered ferromagnetic samples of La0.7Sr0.3-xAgxMnO3 (x = 0.05, 0.25) have been measured at room temperature (<Tc) over frequency interval 1KHz to 15MHz and in presence of magnetic field up to 4KOe. The field dependence of relative change in resistance is small in KHz region but increases strongly for higher frequency of excitation. The maximum value of relative change in resistance at H =4KOe was found to be around 70% at 15MHz frequency.On the contrary the corresponding change in reactance has less frequency sensitivity and the maximum occurs at 1MHz frequency. The magneto-impedance is negative for all frequencies. The normalized magneto-impedance as defined by [Z(H)-Z(0)]/[Z(0)-Z(4K)] when plotted against scaled field H/H1/2 is found to be frequency independent ; H1/2 is the field where normalized magneto-impedance is reduced to half its maximum. A phenomenological formula for magneto-impedance Z (H) in ferromagnetic material is proposed based on Pade approximant. The formula for Z (H) predicts the scaled behavior of normalized magneto-impedance.
Systematic measurements of stress impedance (SI) and magneto-impedance (MI) have been carried out using Co-rich amorphous ribbons of nominal composition Co71-xFexCr7Si8B14 (x = 0, 2) at various excitation frequencies and bias fields and at room temperature. The impedance, Z, for both the samples was found to be very sensitive functions of applied tensile stress (up to 100MPa) exhibiting a maximum SI ratio as much as 80% at low frequency ~ 0.1MHz. The nature of variation of impedance, Z, changes with the excitation frequency especially at higher frequencies in MHz region where it exhibits a peak. Magnetization measurements were also performed to observe the effects of applied stress and magnetization decreases with the application of stress confirming the negative magnetostriction co-efficient of both the samples. Both the samples exhibited negative magneto-impedance when the variation of Z is observed with the applied bias magnetic field, H. Maximum MI ratio as large as 99% has been observed for both the samples at low fields ~ 27Oe. The impedance as functions of applied magnetic field, Z(H), decreases with the application of stress thus making the MI curves broader. Based on the electromagnetic screening and magnetization dynamics and incorporating the Gilbert and the Bloch-Bloembergen damping and stress dependent anisotropy, the SI has been calculated and is found to describe well the stress and field dependence of impedance of the two samples.
The resistive and reactive components of magneto-impedance (MI) for Finemet/Copper/Finemet sandwiched structures based on stress-annealed nanocrystalline Fe75Si15B6Cu1Nb3 ribbons as functions of different fields (longitudinal and perpendicular) and frequencies have been measured and analyzed. Maximum magneto-resistance and magneto-inductance ratios of 700% and 450% have been obtained in 30-600 kHz frequency range respectively. These large magneto-resistance and magneto-inductive ratios are a direct consequence of the large effective relative permeability due to the closed magnetic flux path in the trilayer structure. The influence of perpendicular bias fields (Hper) in the Longitudinal Magneto-impedance (LMI) configuration greatly improves the MI ratios and sensitivities. The maximum MI ratio for the resistive part increases to as large as 2500% for Hper ~ 1 Oe. The sensitivity of the magneto-resistance increases from 48%/Oe to 288%/Oe at 600 kHz frequency with the application of Hper ~ 30 Oe. Such high increase in MI ratios and sensitivities with perpendicular bias fields are due to the formation the favourable (transverse) domain structures.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
