Bit-shifts of recorded magnetization have been investigated using a magnetic force microscope (MFM) for a perpendicular recording medium when exposed to perpendicular magnetic fields at various sample temperatures (RT-200°C). The bit-shift is measured as a position difference of magnetization transition which is estimated from the differentiated MFM line intensity profile observed for a same pair bits before and after exposure to a magnetic field. It is shown that the critical magnetic field above which bit-shift starts to be observed decreases drastically while the bit-shift length increases with increasing the sample temperature. The variation of bit-transition-shift along the recorded track center as well as along the edge can be precisely measured by using the method.

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  We investigated how to control the nano-pinhole structure of a confined-current-path current-perpendicular-to-plane giant magnetoresistive (CCP-CPP GMR) sensor by inducing pulse current. We found an improved MR ratio with reduced sensor resistance by applying an optimal pulse current. This was assumed to be due to the enlarged nano-pinhole area and reduced pinhole resistance. When excessive pulse current was applied, the MR ratio and sensor resistance decreased because the CPP-GMR sensor degraded thermally.

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  A Nano-Granular In Gap Magnetic Sensor (GIGS) constructed of both (Co-Fe)-(Mg-F) nano-granular TMR film and a yoked pair of soft magnetic films has been developed but has greater disadvantages in thermal stability than that of the TMR film itself. The authors assumed that the degradation in GIGS thermal stability was due to the inter-diffusion between TMR film and Si-O film to insulate adjacent structures in GIGS. Mg-F thin film in this study, which was the main component of the TMR film, was attempted as a barrier layer against inter-diffusion. As a result, the thermal stability of GIGS with an Mg-F thin film barrier layer was actually comparable with that of TMR film. The Auger electron spectroscopy profiles revealed that the barrier layer suppressed inter-diffusion.

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  For use of the Moving model as the improved Preisach model, there is a problem to decide the field parameter of sample material. In this paper, a method using minor loop permeability is proposed as an experimental decision one for the field parameter. It is shown that this method for hard magnetic materials is effective like the method used the Preisach diagram divided to two areas, another experimental decision one. Corresponding with values of the field parameter from the experimental two methods, the validity of the method using minor loop permeability could be confirmed.

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  La_2/3Sr_1/3Mn_1-xCu_xO_3-β (LSMC perovskite) ceramic samples were prepared by using a polymerized complex method. Their magnetization under a 100-Oe DC magnetic field steeply changed in the vicinity of Curie temperature T_c, which linearly decreased with increasing Cu content, x. When the LSMC samples were kept in a starch paste and exposed to an alternating magnetic field (40 Oe-rms and 1 MHz), the temperature of the paste was increased and stabilized at a temperature that corresponded well with the T_c of the LSMC perovskite. The stabilized temperature did not change much (e.g., from 38 to 42°C when the field strength increased from 20 to 50 Oe.) compared to conventional ferromagnetic materials whose magnetization does not change abruptly. The LSMC perovskites show promise as materials for heating mediators that have temperature-self-controlled magnetic hyperthermia.

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