Richard H. Dee

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.

Thermal effects in shielded MR heads for tape applications

The authors discuss some factors that limit the permissible input power in multi-track magnetoresistive (MR) tape heads. The possible consequences of increasing the power dissipation in MR heads as a means of increasing readback signal amplitude are discussed. A simple model to describe the temperature rise of a shielded MR element is given. Evidence for exceeding the Curie point of ferrite used in shielded MR heads is seen with element temperatures in excess of 340 degrees C recorded prior to element burnout. >

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.

Magnetic tape recording technology and devices

Magnetic tape recording for data storage is reviewed with respect to the rapidly advancing areal density of recorded data on tape. The key to these advances lies primarily in the ability of heads and media to support this growth, coupled with a move to active track following servo control and advanced recording channels. Multi-element magnetic head devices in the form of arrays of thin film record (write) heads using high moment soft magnetic materials and multilayer magnetoresistive (MR) readback devices are emphasized.

Comparison of MR and GMR spin valve heads for magnetic recording on MP tape

Summary form only given. The use of the giant magnetoresistive (GMR) spin valve (SV) sensor is now pervasive in production disk drives. However, the use of spin valves in tape remains noticeably absent. This is predominantly because the media properties and areal densities currently used in tape are considerably different to those in disk. The tape media thickness and thus moment-thickness product (M/sub r//spl delta/) dominates the recording in tape. The large flux levels emanating from the longer wavelength recordings in RLL recording codes drive the recording method (write equalization) and the read head design characteristics. MR sensors in the form of soft adjacent layer (SAL) biased devices and dual stripe (DSMR) structures are presently used in production tape systems, which together with write equalization give high signal amplitudes at short wavelengths with little or no element saturation at long wavelengths. Another difference between tape and disk systems is the multi-channel read-while-write function giving the unwanted parasitic feedthrough (or cross-feed) noise. It is tape specific noise sources such as this that drive the need for more raw signal amplitude off the tape even though the areal density of present and future tape systems does not approach that of current disk systems. The paper compares a 20 /spl mu/m wide DSMR head with a 4 /spl mu/m wide spin valve similar to that used in disk systems for tape applications.

Effect of magnetostriction on bias fields in self‐biased MR heads

The effect of magnetostriction on the bias conditions in self‐biased magnetoresistive (MR) heads is reported. In self‐biased MR heads where the bias field is derived from the sense current, the optimum bias point is where the head delivers the maximum output per unit input current. The optimum point depends on the element and head geometry, demagnetizing effects, and the permeability of the MR film. During head construction and operation the MR film is subjected to various sources of stress which can directly affect the permeability of the film and thus the position of this optimum bias point. Many self‐biased MR heads were fabricated using MR elements made from thin (<1000 A) oriented NiFe films with the magnetostriction coefficient close to but varied around zero. The results show quite a marked effect and a correlation between as‐deposited measurements and completed device performance. When the magnetostriction is negative the bias current has to be driven to higher values to achieve the defined optimu...

Advanced MR read/inductive write heads for high performance, high density tape applications

Multi-track magnetic tape heads for use in high performance, high density storage subsystems are going through a rapid period of change in response to the continuing demand for increased capacity and data transfer rate. The luxuries of wide read and write tracks and low coercivity media have disappeared, increasing the problem posed for tape head design and manufacturing. The multi-track nature of the head is becoming more complex with the move to full thin film write head structures akin to the thin film disk head. The dramatic increases in track density while maintaining interchange requirements are resulting in significant dimensional reductions in the magnetoresistive (MR) read devices. The increasingly complex new heads dictate stringent process control and correspondingly more lenient head designs in order to achieve an acceptable yield. This paper summarizes the technology transition and the factors that drive those head changes from the media type and track density issues to the recording density and recording code advances.

Read heads for magnetic tapes

Read heads for use with magnetic tape in the past have used magnetic inductive devices. More recently however there has been a migration to magnetoresistive flux sensing devices using primarily the anisotropic magnetoresistance (MR) effect in thin permalloy stripes. High end digital data tape storage systems currently use arrays of MIR read heads for parallel track readback of magnetic transitions on tape. With the rapidly increasing track and bit density, the higher output afforded by MIR sensors and the ability to readily form them into multi-track arrays has made them the device of choice for tape read heads in digital magnetic recording. Both inductive and MIR read heads are reviewed here with discussion on the various types and design issues with an emphasis on MIR heads. In the near future it is envisaged that the recently discovered giant magnetoresistance (GMR) phenomena will be implemented in read heads in both tape and disk applications for very high areal density magnetic storage.

Dependence Of Barkhausen Noise On Material Parameters In Shielded Mr Heads

Barkhausen discontinuities in read waveforms from shielded magnetoresistive (MR) heads have been isolated and analyzed using histograms and statistical methods. The data obtained have been found to be dependent on the test conditions and previous magnetic histories in addition to the magnetic properties of the element. For the heads studied, the Barkhausen noise is found to be affected primarily by easy axis misorientation, input flux excitation amplitude, element aspect ratio, and magnetic history and less so by magnetostriction coefficient. >

Effect of azimuth angle and bias field on second harmonic distortion in differentially biased MR heads

Measurement of the azimuth dependence of the second harmonic distortion (SHD) in magnetoresistive (MR) heads is presented. The use of differential biasing and sensing is one method of eliminating SHD by perfect cancellation of distortion signals from two half-elements oppositely biased. However, when some azimuth angle between the MR element and recorded signals is introduced, the SHD rapidly increases due to an imbalance in the input signal strength for each half-element. The effect of bias field and data on single end biased elements is given. >