Amorphous CoNbZr Films Research Articles

A Measurement of Magnetocardiogram (MCG) by Planar Type Sensor using CoNbZr Film

We developed a very sensitive high-frequency carrier-type magnetic-field sensor with a sub-pT resolution using a transmission-line-type sensor. Meander-type sensor elements using amorphous CoNbZr films (4μm in thickness), Cu conductor with a meander pattern (30 mm in length, 1.0 mm in width, 18 μm in thickness), and a ground plane were fabricated. We obtained a magnetic field resolution of 9.1×10-13 T/Hz1/2 at 1 Hz. The detectable magnetic field was limited by the 1/f noise. We detected a magnetocardiogram (MCG) signal of heartbeats with the sensor.

高周波キャリア型薄膜磁界センサを用いた心磁界測定

We developed a very sensitive high-frequency carrier-type magnetic field sensor with a pT resolution using a transmission-line-type sensor. Meander-type sensor elements using amorphous CoNbZr films were fabricated. We obtained a magnetic field resolution of 3.0 x 10-12 T/Hz1/2 at 1 Hz. The detectable magnetic field was limited by the 1/f noise. We detected the magnetocardiogram (MCG) signal by using the sensor.

Tb doped CoNbZr soft magnetic films with high anisotropy field for applications in GHz frequency region

Abstract CoNbZr films for an adjustable magnetic anisotropy field H k by doping with rare-earth of different atomic ratio Tb element were obtained in this work. The effect of Tb addition ranged from 0 to 4 at.% on the magnetic properties of the amorphous CoNbZr films was further investigated. The results show that the magnetic anisotropy field H k increases sharply with the addition of Tb while the coercivity H ch along the hard axis and H ce along the easy axis change slightly with increasing Tb content in the films. As a consequence, CoNbZr film doped with 2 at.% of Tb exhibits excellent soft magnetic properties with a saturation magnetization 4 πM s of 8.9 kG, a hard axis coercivity H ch of 1.79 Oe, a easy axis coercivity H ce of 1.4 Oe and a magnetic anisotropy field H k of 87 Oe. The measured ferromagnetic resonance frequency f FMR of this film is 2.30 GHz. The real permeability μ ′ is about 100, which is maintained up to 2 GHz. In addition, there is a broad band of the imaginary permeability μ ″ over a large frequency band, indicating high losses. Therefore, Tb doped CoNbZr film is an excellent candidate for high frequency applications such as electromagnetic interference suppressors.

１０｀−１３´Ｔ台の磁界検出分解能を有する高周波伝送線路型薄膜磁界センサ

We developed a very sensitive high-frequency carrier-type magnetic field sensor with a sub-pT resolution using a resonating transmission line. Meander-type sensor elements using amorphous CoNbZr films were fabricated. We obtained a magnetic field resolution of 7.4 x 10-13 T/Hz1/2 at 501 kHz. The detectable magnetic field was limited bythe noise caused by nonlinear magnetic excitation. We analyzed the quality factor of the resonance for enhancementof the signal-to-noise ratio.

反射信号を用いた高周波キャリア型磁界センサによる微小交流磁界計測に関する研究

The high-frequency carrier-type (HFC-type) magnetic field sensor realizes very high sensitivity without any cooling apparatus for the sensor element. An important technique for obtaining high sensitivity is the use of a high-frequency current applied to the sensor element. The maximum sensitivity is obtained at frequencies up to the ferromagnetic resonance of the sensor magnetic thin film; for example, hundreds of megahertz for amorphous CoNbZr films. It is becoming important to study high-frequency circuits for driving HFC-type magnetic field sensors in order to achieve any practical applications such as nondestructive testing or biomedical applications. In this paper, a method of reflection signal measurement is studied in order to measure alternating magnetic fields with very small magnitude. A theoretical formula based on an equivalent circuit model was obtained for the relation between the sensor property and measurement sensitivity. An experimental confirmation was carried out by comparing this formula with experimental results. Finally, the measurement of a small alternating magnetic fields was effected by combining reflection signal measurement with the carrier-suppressing method.

Effect of Pd addition on the magnetic characteristics of amorphous CoNbZr films

The goal of the present paper is to investigate the phase stability and soft magnetic properties of amorphous CoNbZr films when Pd is added. The CoNbZrPd films deposited on Si wafers exhibited amorphous structures independent of the amount of Pd. On the addition of 4.34% Pd, excellent soft magnetic characteristics of the films were observed with a coercive force of 0.54 Oe and an anisotropy field of 11 Oe, whereas a coercive force of 1 Oe and an anisotropy field of 3.5 Oe were shown in the film without the addition of Pd. The increased anisotropy field and low coercive force of the films may be attributed to the occupancy of Pd in preferred sites parallel to an external magnetic field applied during the deposition process. A permeability of about 1100 was constant at operation frequencies ranging up to 100 MHz, which can be explained by the Landau–Lifshitz formula.

Domain wall pinning and hysteresis losses in amorphous CoNbZr films

In a series of CoNbZr amorphous films prepared by RF sputtering, with thickness t ranging from 86 to 480 nm, the authors show that the domain wall (DW) motion is the dominant magnetization mechanism in the irreversible processes when the magnetic field is applied along the in-plane easy axis. A simple model, assuming a DW pinning at the film surfaces, explains the existence of a critical unpinning field (as well as hysteresis losses) inversely proportional to the film thickness. Frequency effects in loop parameters are reported up to 100 kHz.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Sputtered sandwich heads for high-density digital video recording

A sandwich type of head for application in high-frequency and high-density digital video systems is described. Amorphous CoNbZr films laminated with an Al/sub 2/O/sub 3/ insulator layer are used as core material. The influence of rotating and static field annealing on the domain structure and on the permeability is discussed. In order to achieve a sufficiently high efficiency, a polycrystalline ferrite back yoke is applied. Sandwich heads with several ceramic materials in the contact plane are evaluated. The performance of the heads is investigated on the basis of a signal-to-noise criterion, defined specially for the digital video application. A sandwich head made with 2 mu m*5 mu m amorphous CoNbZr, laminated with 0.1 mu m Al/sub 2/O/sub 3/, between glass-ceramic substrates fulfils the requirement on MP tape. >