Transverse Giant Magnetoimpedance Research Articles

Experimental Study of the Bias Direct Currents on the Transverse Giant Magnetoimpedance Effect in a Soft Ferromagnetic Microwire

This paper reports on an experimental study of influences of the bias direct currents on the transverse giant magnetoimpedance effect in a FeCoNiBSiMo microwire. Along with increasing the bias direct currents, the low field sensitivity of the impedance increases evidently at high frequency (10–120 MHz). The low field sensitivity (4 Oe) by presence of 30 mA of bias direct currents is about 3 times larger than that without using bias direct currents at 60 MHz. However, the high field sensitivity of the impedance decreases by use of bias direct currents at high frequency. In addition, the low field linearity is improved by use of bias direct currents at high frequency. The experimental results could be very useful for the design of multi-dimensional giant magnetoimpedance sensors with high low field sensitivity and linearity.

Preparation of a SiO 2 ‐covered amorphous CoFeSiB microwire and study on the current amplitude effect on the transverse giant magnetoimpedance

A SiO2-covered amorphous wire was prepared by the melt spinning technique for investigation of the current amplitude effect on the giant magnetoimpedance (GMI). The raw alloy (CoFeSiB) was placed in a SiO2 tube and heated by induced current (600 A) for 50 s, then the SiO2-covered amorphous wire was formed through external traction and cooling water. The current amplitude effects on the transverse GMI, giant magnetoresistance (GMR) and giant magnetoreactance (GMX) in the SiO2-covered amorphous CoFeSiB wire were studied thoroughly. It was observed that the transverse GMI ratio, GMR ratio, and GMX ratio all increase with decreasing the current amplitude, demonstrating the possibility of using them to design low-consumption, high-sensitive and muti-dimension magnetometer.

Giant Magnetoimpedance Effect in a Sandwiched Structure of as-Quenched FeNiCrSiB Ribbons

The giant magnetoimpedance (GMI) effect and effective permeability ratio in a QFR/Cu/QFR sandwiched structure are studied, where QFR stands for the as-quenched FeNiCrSiB amorphous ribbon. Remarkable GMI effects are obtained in the QFR/Cu/QFR sandwiched structure without annealing. The maximum values of the longitudinal and transverse GMI ratios at 0.5 MHz are 282% and 408%, respectively. Correspondingly, the maximum effective permeability ratios at 0.5 MHz are 326% and 1013% in longitudinal and transverse field, respectively. These large GMI values are attributed to the high effective permeability of the sample due to the closed alternating current (ac) magnetic flux path in the sandwiched structure, and large permeability variation induced by the magnetic field.

Transverse, longitudinal and perpendicular giant magnetoimpedance effects in a compact multiturn meander NiFe/Cu/NiFe trilayer film sensor

A compact multiturn meander NiFe/Cu/NiFe trilayer film giant magnetoimpedance (GMI) sensor, with the width of 100 µm for NiFe film and 60 µm for Cu film, the space of 40 µm and a turn number of 10 is fabricated by the MEMS technique on a silicon substrate. The transverse, longitudinal and perpendicular GMI effects are respectively investigated in the magnetic field range of 0–120 Oe and the frequency range of 1–40 MHz. With the magnetic field it could be up to 86.6% for the transverse GMI effect at 15 MHz and 120 Oe, 166% for the longitudinal GMI effect at 15 MHz and 20 Oe and 165% for the perpendicular GMI effect at 10 MHz and 50 Oe. In addition, there are platform stages, which correspond to the magnetic field range of 0–20 Oe for the transverse GMI effect and 0–10 Oe for the perpendicular GMI effect. Furthermore, the peak of GMI effects covers a large frequency range, which could be up to about several tens of MHz. The GMI platform and the strong GMI effect could be attributed to the demagnetization effect and enhanced electromagnetic coupling from the compact meander sensor structure, respectively. The broad frequency peak originates from the different magnetization process in the straight segment in the meander structure.

Influence of Different Annealing Process on the Giant Mageto-impedance Effect of FeZrBCu Films

Influence of different annealing process on the giant magneto-impedance(GMI) effect in soft magnetic alloy films of(Fe88Zr7B5)0.96Cu0.04,which were prepared by radio frequency(RF) sputtering,was studied.It is obtained that both natural and current annealing can reduce the longitudinal GMI ratio.And the longitudinal GMI ratio of the annealed films increases with the increase of annealing current,and reaches a maximum value of 17% at 800mA,while the sensitivity increase to 7%(kA/m)-1 at such annealing current(800mA).In addition,influence of the magnetic field annealing on GMI effect is discussed.It is found that both the longitudinal and transverse GMI ratios of the films after magnetic field annealed increase at different temperatures.There exists a critical temperature(250℃),at which the longitudinal GMI ration presents a single-peak with a value of 17.5%,while the transverse one presents a double-peak with a value of 17.8% at ±0.4kA/m.

Giant magnetoimpedance effect of multilayered structure (F/SiO2)3/Ag/(SiO2/F)3 films deposited in a longitudinal magnetic field

The soft magnetic properties and giant magnetoimpedance (GMI) effect of the multilayered structure (F/SiO2)3/Ag/(SiO2/F)3 (F≡Fe71.5Cu1Cr2.5V4Si12B9) films, which were prepared by radio frequency sputtering without and with a longitudinal magnetic field of about 72 kA/m, are studied. The results show that the GMI effect almost cannot be detected in the samples deposited without field, whereas, a longitudinal magnetic field applied during deposition process obviously optimizes the soft magnetic properties of the films, and noticeable GMI effect is obtained. The maximum values of the longitudinal and transverse GMI ratios are 45% and 44% at the frequency of 6.81 MHz, respectively. In addition, the dependence of magnetoimpedance ratio, magnetoresistance ratio, magnetoreactance ratio and effective permeability ratio on the frequency has been investigated. We found that the GMI spectrum curves in the longitudinal and transverse cases almost overlap for the field-deposited sample. The GMI effect is mainly a giant magnetoinductive effect at low frequencies. When f >9 MHz, magnetoreactance ratio changes to a negative, i.e., the property of reactance changes from inductive to capacitive.

Giant magnetoimpedance effects in patterned Co‐based ribbons with a meander structure

AbstractLongitudinal and transverse giant magnetoimpedance (GMI) effects in micropatterned ribbons (Metglas® 2714A) with meander structure are investigated. The maximum longitudinal GMI ratio of the ribbons is 180.4% and it presents to HL = 10 Oe and an AC frequency f = 20 MHz. In the range of 0–10 Oe, the GMI sensitivity of ribbons is 8.1%/Oe at 20 MHz. The maximum transverse GMI ratio is much less than the longitudinal one and the position of GMI extreme value is corresponding to higher magnetic field. The difference between the longitudinal and the transverse GMI effect is due to two main reasons: one is the easy axis deviates from the transverse direction of the sample; another is the demagnetizing factor D⊥ effect on the longitudinal permeability. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Transverse giant magneto-impedance effect in FeCuCrVSiB single layered and multilayered films

Magnetic properties and giant magneto-impedance (GMI) effects of FeCuCrVSiB single layered and multilayered films with Ag as the central layer and SiO2 as the isolating layers, which were prepared by radio frequency sputtering without field and with a magnetic field about 72kA/m along the films length, are investigated. The hysteresis loops of single layered films show that the samples deposited with a magnetic field possess excellent soft magnetic properties and the coercive force is only about 64A/m. After annealing at an optimum temperature of 230℃ for 1.5h, the maximum GMI ratios of single layered films are 37.5% in transverse field at the frequency of 13MHz, and the maximum GMI ratios of multilayered films is 277% at the frequency of 8.6MHz. The frequency dependence of the magneto-impedance indicates that the GMI effect in multilayered films can be very large even at relatively low frequencies.

Giant magnetoimpedance in multilayered Fe71.5Cu1Cr2.5V4Si12B9 films

Giant magnetoimpedance (GMI) effects were studied in multilayered films with a structure of (F/SiO2)3/Ag/(SiO2/F)3, where F represents the amorphous soft ferromagnetic layer having a composition of Fe71.5Cu1Cr2.5V4Si12B9. The samples were deposited by radio-frequency sputtering under an applied magnetic field of 900 Oe in the plane of the film and then annealed at an optimum temperature of 230°C for 1.5 h. Longitudinal and transverse GMI ratios of up to 251% and 277% were obtained at a frequency of 8.5 MHz. Maximum GMI sensitivities of 12.5% Oe−1 and 9.2% Oe−1 were achieved in longitudinal and transverse fields, respectively. For the as-deposited state, the maximum GMI ratios were about 45% and 44% in the longitudinal and transverse cases, respectively. These values are much higher than those obtained for FeCuCrVSiB/Ag (or Cu)/FeCuCrVSiB sandwiched films. These very large GMI responses are attributed to the superior soft magnetic alloy and SiO2 layers used in the magnetic layers and the magnetic field used in the preparation process.

Magnetic Properties and Giant Magneto-Impedance in Nanocrystalline FeCuCrVSiB Films

The giant magneto-impedance (GMI) effect has been observed in nanocrystalline FeCuCrVSiB films prepared by rf sputtering followed by an annealing treatment. The magnetic properties and the longitudinal and transverse GMI have been studied in detail. Field dependence and frequency spectra of GMI effect have been studied in the frequency range from 100 kHz to 13 MHz. Maximum GMI ratios as large as 50% and 25% were obtained at 13 MHz in the longitudinal and transverse cases, respectively. The field sensitivity of the longitudinal GMI is about 0.11% m/A at 13 MHz. The dependence of effective permeability on the frequency and magnetic field has been investigated.

Giant magnetoimpedance and domain structure in FeCuNbSiB films and sandwiched films

Longitudinal and transverse giant magnetoimpedance (GMI) effects are studied in FeCuNbSiB and FeCuNbSiB/Cu/FeCuNbSiB films. In regard to as-deposited single layer films, hardly any GMI effect can be detected, while for as-deposited sandwiched films, the maximum GMI ratios of 32% and 11% are obtained in longitudinal and transverse fields, respectively. After annealing, the maximum GMI ratios of 18% and 14% are obtained for the single-layer films in longitudinal and transverse cases, while for the sandwiched films, the maximum GMI ratios are 67% and 80% in longitudinal and transverse cases, respectively. A giant magnetoinductance ratio as large as 1733% is obtained in annealed sandwiched films at a low frequency of 100 kHz. In order to know the relation between GMI effect and magnetic properties of the samples, the domain structures are observed by the Kerr effect.

Magneto-Impedance in Fe73.5Cu1Mo3Si13.5B9 Alloy Ribbons

Giant magneto-impedance (GMI) effects in Fe73.5Cu1Mo3Si13.5B9 alloy ribbons have been measured under different external magnetic fields and different ac driving current frequencies. The results show that the longitudinal and the transverse GMI change with the annealing temperature. Based on the classical electromagnetic theory, the difference between the longitudinal and the transverse GMI (R,X,Z) has been discussed in this letter.