James C. Cates

Advanced multi-track tape head for high performance tape recording application

A recently developed, advanced multi-track tape head for operation in a next generation, high performance tape drive is described. This head features full thin film write elements with high moment, cobalt-based pole materials for recording on high coercivity metal particle (MP) tape, together with narrow track, shielded, dual-stripe magnetoresistive (DSMR) read elements. This presentation will discuss the global design philosophy of the head with particular attention to the design and recording performance of the read and write elements in a tape environment. The bead is capable of recording 288 tracks on half-inch, MP tape of 1625-1850 Oe coercivity at a recording density of 65 kfci. The system operates with 16 parallel data channels and includes full multi-element active track following servo. The head can be used in a full start-stop mode and read verify on the fly (read-while-write) bi-directional operating modes.

Crosstrack profiles of thin film MR tape heads using the azimuth displacement method

We report a new technique for measurement of crosstrack profiles of magnetoresistive (MR) read elements in tape heads. This method minimizes errors due to tape tracking and quickly delivers crosstrack profiles with good signal-to-noise ratios. In this technique the read element is located downstream from the write head in a typical tape head configuration. AC erased tape is passed over the head and the write head is turned on. The profile of the read element is scanned by changing the lateral position of the read element relative to the write head by varying the azimuth angle between the head and tape with a positioner. Offtrack position is calculated from the linear displacement of the positioner used to generate the azimuth angle. The measurement technique is well suited for characterizing MR read heads for tape servo applications and for examining performance reliability and repeatability.

Measurement of head wear rates using custom high sensitivity electrical elements

A technique for measuring the wear rate of a tape recording head is described that can produce a theoretical dimensional resolution of 0.02 nm. Custom four wire elements are located in the gap of the actual recording head design to be tested (rather than using substitutes) and can be strategically placed to measure the wear rate across the width of the tape. Temperature compensation is achieved by measurement of a spare identical element in the head structure set back from the wear surface such that it does not receive wear. The wear rate at various locations across the head gap lines of NiZn ferrite heads have thus been obtained continuously as a function of the amount of CrO/sub 2/ tape passed and show that the wear rate is greater near the tape edges. Due to the high sensitivity of the test elements, use of long reels of tape and placement of multiple heads in the same tape path, comparisons of head contour shape and/or materials can be made in a very short test time. >

Measurement of magnetostriction in self-biased shielded magnetoresistive heads

We report a method of measuring the magnetostriction of self-biased shielded magnetoresistive (MR) elements. In this technique the optimum bias current for the MR element, defined as the point where the head delivers the maximum output per unit current, is determined by measuring the head output from a flux source while varying the bias current fed to the element. A mechanical fixture is then used to bend the head and strain the MR film. Because of magnetoelastic effects, the change in stress alters the MR element anisotropy and causes a shift of the optimum bias point. The optimum bias point is measured as a function of the stress applied to the MR element and the dependence modeled using a nonlinear transmission-line model for a shielded MR head with shunt and/or offset bias. Parameters for the model are set by fitting the full output voltage versus bias current curve. The changes in the value of the MR element anisotropy required to fit the experimental data are attributed to changes in the magnetoelastic anisotropy and the magnetostriction calculated. This measurement technique does require the removal of one of the shields in order to guarantee a uniform and reproducible strain of the MR film when the head is bent. >