半導体薄膜のHall効果を応用した磁気再生ヘッド
1968 年 24 巻 6 号 p. 365-371
詳細
1968 年 24 巻 6 号 p. 365-371
Reproducing heads commonly used for magnetic tape recordings are sensitive only to the rate of change of magnetic flux in the tape, so that its most important basic characteristic is the frequency response: as the frequency decreases the output falls off in proportion and reaches zero at zero frequency. The characteristic is shown in fig. 5(a). In order to compensate for the drop at low frequencies, the amplifiers for usual winding heads require a bass-boost amounting to 30〜40 dB at 30 Hz. The winding heads are not suitable for those applications which require very low frequency response, such as data analysis. The output frequency response of the Hall-effect heads is essentially flat from d-c to ultra high frequencies, as in shown in Fig. 5(b). Today, microminiaturization of these heads are required. In this regard, the winding heads are limitative in size and the Hall-effect heads are the most suitable. After all Hall-effect heads are most excellent in respect to frequency response and size miniaturization, but the preparation of Hall-effect heads requires semiconducting thin film Hall elements with very high characteristics comparable to those of semiconductor single crystals. The author has investigated Indium-Antimonide thin films and recently has succedded in obtaining thin films with high physical characteristics(R=200〜300 cm^3/c, μ_e=40, 000〜50, 000 cm^2/Vン). They have been utilized in the preparation of the front gap type Hall-effect heads. In this instance, the most suitable thickness of the film was found to be 0. 9μ. Permalloy was used a the magnetic circuit material. The thin film Hall element which was evaporated on a mica surface is shown in Fig. 8(a), the assembled head is shown in Fig. 8(b) and the microscopic photograph of the gap in the magnetic circuit is shown in Fig. 8(c). Frequency responses of different types of heads are shown in Fig. 9((a) net output of the winding head, (b) output of the winding head after equalizer, (c) net output of the Hall-effct head, (d) the same as (c))
