Domain structures in sintered Nd₂Fe₁₄B magnets were studied using Kerr effect microscopy (KEM) and magneto-force microscopy (MFM). In the direction perpendicular to the crystal c-axis (c-plane), a fine maze domain structure was observed using KEM, but an only unclear complex structure can be obtained using MFM. After 5T pulse magnetization, both observation methods gave clear monotonous images of many magnetized grains and local fine domain structures with strong contrast in limited numbers of grains. On the other hand, in the direction of parallel to the c-axis (in a sense, a-plane), only bright or dark grains as a whole grain, were observed using both methods. These observations can be explained as that the surface demagnetized grains have a role of permeable medium of the magnetic fluxes from the inner domains. As a conclusion, when the inner grains generate sufficient magnetic fluxes to magnetize the surface no-coercive grains, the inner domain structures of the sintered Nd₂Fe₁₄B magnets can be observed using KEM and MFM.

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This paper describes the detection of conductive microbead by spin-valve giant magnetoresistance (SV-GMR) with ferrite core exciter base on eddy-current testing (ECT) technique. The single and row conductive microbead were detected by the proposed ECT probe. The six microbeads were 125, 150, 200, 250, 300 and 360 μm radiuses. The three model of single row was slightly pitched in each row with range from 400 to 1000 μm. The analytical methods were calculated that confirmed the experimental result. The comparison of reference and proposed ECT probe signal variation with signal to noise ratio were expressed. The experimental results show that the proposed ECT can clearly detect both single and row conductive microbead position.

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The magnetic field distributions around slave media with and without SUL were calculated by using the finite element method to estimate what influence a soft-under-layer (SUL) in a double-layered perpendicular medium had on magnetic duplication characteristics. As a result, we found the SUL enhanced duplication characteristics for any bit length and track width. The SUL in bit printing influences the duplication characteristics more than that in edge printing. The influence of SUL on duplication characteristics in bit printing increases as the strength of the duplication field increases. However, in edge printing, there is a duplication field that maximizes the influence of SUL on duplication characteristics. Moreover, the influence of SUL on duplication characteristics decreases with both bit and edge printing as bit the length of the magnetic pattern decreases, and also decreases as the track width decreases. These dependencies can be explained by taking the demagnetization coefficient of SUL and the total amount of magnetic charge appearing in SUL and magnetic patterns into account.

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Experiments on perpendicular magnetic contact duplication by using enlarged models were conducted, where we investigated what influence the strength of the duplication field and the magnetic layer thickness of the master had on duplication characteristics. Excellent duplication characteristics were obtained with bit printing when the duplication field was around the value of the coercivity of the slave, and the duplication characteristics improved as the magnetic layer of the master became thicker. In edge printing, the duplication characteristics improved as the duplication field was increased up to a certain field strength, above which the characteristics saturated, and barely depended on the thickness of the magnetic layer in the master. When their duplication magnetizations were compared, edge printing was more advantageous than bit printing.

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Crystallographic orientation of the MgO barrier in sputter-deposited CoFeB/MgO/CoFeB magnetic tunnel junctions (MTJs) and its effect on tunnel magnetoresistance (TMR) were investigated. The degree of MgO(001) orientation was estimated with the integral intensity ratio (I ₍₂₀₀₎ /I ₍₂₂₀₎) of diffraction lines from MgO(200) and MgO(220) planes obtained in grazing incident x-ray diffraction profiles. The main results are stated as follows. (1) I ₍₂₀₀₎ /I ₍₂₂₀₎ ∼ 4, meaning the (001) orientation of MgO, is realized when the underlaid CoFeB maintains amorphous structure, meanwhile MgO on bcc(110)-oriented CoFe shows (111) orientation (I ₍₂₀₀₎ /I ₍₂₂₀₎ = 0). (2) The prevention of epitaxial growth on hcp(00.1)-oriented Ru layer is effective to maintain amorphous structure of CoFeB. (3) The achievable TMR ratio after high temperature (280 °C − 450 °C) annealing is mainly dominated by the MgO orientation and giant TMR ratio exceeding 200% is only obtained with I ₍₂₀₀₎ /I ₍₂₂₀₎ ≥ 3.4, while the resistance area product is independent of I ₍₂₀₀₎ /I ₍₂₂₀₎. (4) Thin Mg layer inserted between CoFeB layer and MgO barrier is effective to obtain bcc(001)-oriented crystallization of CoFeB after high temperature annealing and results in a giant TMR ratio, because of its role to avoid surface oxidization of underlying ferromagnetic electrode during the deposition of MgO barrier.

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A typical magnetically shielded room (MSR) for an electron beam lithography system and biomagnetic measurements is composed by multi-layered ferromagnetic materials such as μ-metal. However, a number of openings must be provided in the wall and floor for air conditioning and cables. In this paper, the optimal structure of a duct to prevent leakage flux from entering through the openings was investigated by 3-D magnetic field analysis. We found that the duct should be connected to the inner layer in order to reduce the introduction of the leakage fluxes from the middle and outer layers. When magnetic noise is applied vertically to the opening, the duct protruding from the outer layer should be short, in order to avoid gathering surplus fluxes from outside the MSR. Inner partition plates dividing the hole of the duct are also effective for this purpose.

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A new noncontacting current sensor with a compact size was developed on the basis of the magnetic bridge principle. The magnetic bridge utilizes the monotonically increasing portion of the permeability of the core together with the fl ux density. To ensure that the sensitivity of the current sensor is high enough to detect a μA-order current, the magnetic bridge circuit is made in a round shape enclosing a current-carrying conductor. The whole structure of the magnetic bridge current sensor (MBCS) is encapsulated in a thick magnetic shield made of permalloy. The resolution of the current sensor presented in this paper is about 3 μA under an excitation current of 830 μA in 2.5 kHz. Therefore, the interference affecting the measured circuit is reduced to a negligible level.

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