Record characteristics of tape heads with CoZr and NiFe poles

Overwrite and recorded signal are compared for tape heads with Co ₉₁Zr₉ and Ni₈₁Fe₁₉ poles as a function of throat height. The effects of throat height variation on performance are discussed for constant current recording with and without pole saturation. The impact of pole saturation on throat height tolerance is also discussed. Co₉₁Zr₉ and Ni₈₁ Fe₁₉ tape heads have equivalent record performance as long as their poles are not saturated. When pole saturation does affect head performance, it has less impact on CoZr heads, and they record and overwrite better than NiFe heads. In a system that requires at least 25-dB 2f/1f overwrite at 2362 fc/mm (60 kFCI), for example, both CoZr and NiFe heads would perform well on oxide tape over a wide range of throat heights. On metal particle tape the overwrite falls below 25 dB at a throat height of 4.4 μm for the CoZr heads and 2.3 μm for the NiFe heads. These throat height limits could be extended with thicker poles or, in the case of NiFe, plated poles that maintain a uniform thickness on sloped areas of the underlying films. Nonetheless, for the conditions described here CoZr heads had nearly twice the throat height tolerance of otherwise identical NiFe heads