In the case of rigid disk files, improvements in the recording medium and the head are required to increase bit density. This letter reports a high recording density of 2600 bit/mm (65000 bit/i), achieved by using high coercive force (100 Oe) sputtered γ-Fe2O3 thin film media and a narrow gap (2g0.15µm)head.

Gamma ferric oxide thin film media with a thickness of 0.190.27 µm were prepared by a reactive RF sputtering. Signal output loss with increasing temperature at high recording density was studies. Heating a medium-head system to 55 results in a 16% loss of signal output at 790 bpm (D-6 dB) of recording density for a medium having a 0.19 µm thickness; a 40% loss of signal output for a conventional-coated medium having a 0.7 µm thickness at 400 bpm (D-6dB), accompanying a decrease of a saturation write current value, IW(k-1) (an optimum write current). Increments of medium thickness and write current enhanced the thermal signal output loss. An over-saturated recording in the write process was suggested to cause the thermal signal output loss, especially for the thicker media. From the perspective of thermal stability of signal output at high recording density, sputtered γ-Fe2O3 thin film media are advantageous because of their thinness and small write current dependence of signal output.

To realize a highly efficient small antenna, high-Tc superconductors are adopted to fabricate both a self-resonating helical radiator and a quarter-wave matching circuit. The actual gain and bandwidth measured at 478 MHz using a 1/45-wavelength radiator were respectively 1.5 dBi and 0.35%, indicating that this type of antenna has a high radiation efficiency and a fairly wide bandwidth. It is also confirmed through experiments and theoretical simulations that a decrease in the surface resistance of the radiator more effectively improves the radiation efficiency than a decrease in the surface resistance of the matching circuit.

This paper describes a new method for joining BiSrCaCuO superconductors (BSCCO) which realizes low microwave loss and high mechanical strength. This method consists of two processes. In the first the BSCCO surface is metallized with Ag and in the second a joint is formed by using thermally curable Ag paste. With this method, we obtained a joint with a loss of 0.3 dB around 1.1 GHz with the co-axial cavity techniques. Furthermore, the mechanical strength of the joint was greater than that of the BSCCO sample. From the results of DC resistance measurements and SEM observations, we attribute this good performance to the adhesion and continuity of the metallized Ag with the BSCCO surface.