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High-efficiency cavity-dumped ytterbium-doped yttrium aluminum garnet (Yb:YAG) laser was developed. Although the high quantum efficiency of ytterbium-doped laser materials is appropriate for high-efficiency laser oscillation, the efficiency is decreased by their quasi-three/four laser natures. High gain operation by high intensity pumping is suitable for high efficiency oscillation on the quasi-three/four lasers without extremely low temperature cooling. In our group, highest efficiency oscillations for continuous wave, nanosecond to picosecond pulse lasers were achieved at room temperature by the high gain operation in which pump intensities were beyond 100 kW/cm 2 .

A narrow-gap shielded magnetoresistive (MR) head with a 8-,um track width has been constructed for high-density magnetic recording. The head consists of a pair of NiFe shields and a trilayered MR element between the shields. In the MR element NiFe, Ti, and amorphous CoZrMo films are used. The thickness of the three layers and the shields, as wen as the shield gap length, are optimized with a one-dimensional self-consistent calculation. The shielded MR head has been fabricated using calculated thickness parameters for individual layers: 60 nrn for CoZrMo with 40 nm NiFe and 20 nrn Ti, l-pm shields, and 0.5 pm for the total shield gap. The reproduced characteristics from the MR head are evaluated with a plated disk. Neither Barkhausen noise nor distortion is observed in the output waveform. The output voltage is 600 ,uVp!, at a 4 mAI,um sense current with 30 kFCI transition density. The Dso transition density is 40 kFCI. These values are in good agreement with the calculated values. Assuming a 12-,um track pitch, crosstalk is -29 dB from off-track crosstalk characteristics. This shielded MR head has a potential to achieve high recording density with 40 kEPI and 2000 TPI for small-size disk drives.

NiMn antiferromagnets with a high blocking temperature are attractive for application to the pinning layer in spin-valve heads, because a highly stable exchange coupling field is expected through their use. We have fabricated NiMn spinvalve heads having a CoZrTa bottom shield and a CoZrTaNiFe write element, using an anisotropy control process which provides a desirable magnetization configuration in each magnetic layer. These heads showed highly stable, symmetrical, and Barkhausen noise free readback waveforms with output voltage of over 800 pV,&m.