Solid State Phenomena Vols. 152-153

Abstract: Three-dimensional finite element method has been used for modelling of the magnetic field and computation of the electromagnetic force of recently developed permanent magnet linear actuator. The actuator is subject to specific requirements – having four stable positions without supply and maintaining minimum static force during the whole working stroke. The actuator consists of several cores with coils placed on a common yoke and a moving permanent magnet. It is intended for needle driving in a knitting machine. Influence of different factors on the static force characteristic is estimated.

Abstract: We have studied electron magnetic resonance spectra of iron-oxide nanoparticles related to iron reduction metabolism of dissimilatory bacterium Thermincola ferriacetica. It is found that the resonance parameters of metabolic products change notably with time. The X-ray diffraction data indicates partial crystallization of iron oxide during long time storage under air open conditions.

Abstract: Influence of cerium substitution on the valence phase transition in Yb1-xCexInCu4 system (x = 0, 0.04, 0.08, 0.12 and 0.16) has been studied by means of 63Cu NQR. Discontinuous change in Cu NQR frequency was detected around valence transition temperature Tv in YbInCu4, Yb0.96Ce0.04InCu4 and Yb0.92Ce0.08InCu4. In the vicinity of Ce concentration x = 0.08 a crossover from the 1-st order valence phase transition to gradual change of electronic and magnetic properties of Yb1-xCexInCu4 system is observed.

Abstract: high-Tc SQUID, magnetometer, bio-magnetism, multi-channel, rat MCG. Abstract. Three-channel directly-coupled-type high-Tc SQUID magnetometer array, with pick-up coil size of 1.5 mm2 comparable to the lift-off distance of the developed multi-channel SQUID system, was designed. In this design, two slits were introduced in the SQUID ring to improve the inductive coupling between the pick-up coil and the SQUID ring to obtain the field sensitivity of about 700 fT/Hz1/2. With the SQUID array that was mounted on the multi-channel SQUID system, the measurements of magnetocardiogram of rat were demonstrated to evaluate the system performance.

Abstract: Influence of water molecules reversible adsorption on domain structure and domain wall structure in amorphous Fe-rich ferromagnet samples is investigated by magnetooptical method. Before investigation the samples were kept in the air. Domain structure of the samples significantly changes in wacuum: instead one 180-degree domain wall several domain walls appear which are oriented with angle 45o to the long side of the sample. This effect is completely reversible. Another new effect is found: domain wall width on the sample surface in vacuum is 35% bigger (13.5 µm) than in atmosphere of water vapor (10 µm).

Abstract: The kinetics of formation of iron-containing minerals by thermophilic dissimilatory iron-reducing bacteria Themincola ferriacetica (strain Z-0001) has been investigated by Mössbauer spectroscopy. The Mossbauer measurements were performed at room and low (77 and 4.2 K) temperatures and in a magnetic field of 6 T. Electron magnetic resonance (EМR) measurements were also carried out.

Abstract: Heating of a magnetizable body in an alternating magnetic field near the Curie point due to non-equilibrium magnetizing is theoretically investigated. The body is of a spherical shape and surrounded by a non-magnetizable unbounded medium. The heat generation power density is regarded as a piecewise linear function with a fracture at the Curie point. The steady temperature distribution within the body and outside it is found.

Abstract: Electrostatic discharge (ESD) effects on GMR recording heads have been reported as the major cause of head failure. Since the information density in hard-disk drives has dramatically increased, the GMR head will be no longer used. The tunneling magnetoresistive (TMR) read heads are initially introduced for a 100 Gbit/in2 density or more. Although the failure mechanism of ESD in GMR recording head has not been explicitly understood in detail, study to protect from this effect has to be undergone. As the TMR head has been commercially started, the ESD effect is closely watched. This is the first time report of the TMR equivalent circuit in order to evaluate the ESD effect. A standard human body model (HBM) is discharged across R+ and R- where the capacitance of flex on suspension (FOS) is varied. It is intriguingly found that the electrical characteristic of the TMR head during discharge period depends on discharge position. This may be explained in terms of asymmetry impedance of TMR by using adapted Thevenin’s theory. The effect of FOS component on TMR recording head is also discussed.

Abstract: This report proposes the wavelet transform technique using the 4th Daubechies order to detect glitches on a magnetic recording head signal in the time-domain. It is found that the glitch occurs when the electrostatic discharged (ESD) level of the machine model (MM) on giant magnetoresistive (GMR) heads is in the range of 6-9 V. The electrical test parameter and scanning electron microscope (SEM) photograph of recording heads shows no change in reader sensor. However, the parameter and SEM results clearly show the visible GMR damage when the MM-ESD voltage (VESD) is 10 V. The glitch in magnetic response signal of the GMR head occurs when the VESD is increased. Therefore, the wavelet transform technique can be a novel instrument to forecast the GMR degradation due to the MM-ESD effect.

Abstract: This report aims to investigate a comparative effect of Electromagnetic Interference (EMI) on recording heads due to sweeping directions of low-to-high and high-to-low frequencies. Four selected Quasi-Static Tester (QST) parameters; MR resistance, MR amplitude asymmetry, Barkhausen noise and Hysteresis, are used for monitoring the effect of EMI on Head Gimbal Assembly (HGA). It is undoubtedly found that the Asymmetry and Hysteresis parameters provide insufficient indication of EMI effect for both sweeping frequency directions. On the other hand, it is discovered that the sweeping direction of the low-to-high frequency is more effective to two test parameters; MR resistance and Barkhausen noise, than the other direction. The dramatic energy accumulation is possibly explained this phenomenon but this energy level is not high enough to cause the Hysteresis change.