Ching H. Tsang

Design, fabrication and performance of spin-valve read heads for magnetic recording applications

Since the early 1990s, the introduction of dual-element recording heads with inductive write elements and magnetoresistive (MR) read elements has almost doubled the rate of areal density improvements for hard-disk-drive data storage products. In the past several years, prospects of even more rapid performance improvements have been made possible by the discovery and development of sensors based on the giant magnetoresistance (GMR) effect, also known as the spin-valve effect, for a particular class of sensor configurations. In this paper, we explore the potentials as well as challenges of spin-valve sensors as magnetic recording read heads. We first examine the data rate and areal density potentials of large read-back signals resulting from increases in the MR coefficient. We then discuss associated magnetic sensor performance, including linearity and noise suppression. Finally, we study in detail the magnetic and recording performance of a spin-valve read head designed for 1-Gbl/in. 2 density performance.

Spin-valve and tunnel-valve structures with in situ in-stack bias

The use of in-stack longitudinal magnetic stabilization for spin-valve and tunnel-valve recording head sensors has been investigated. An in-stack ferromagnetic layer pinned with an IrMn antiferromagnet is used to magnetostatically stabilize the free layer by flux closure. The use of IrMn with lower blocking temperature than PtMn allows the bias layer to be set independently from the PtMn-pinned reference layer in the spin-valve or tunnel-valve. A Ta spacer 10-30 /spl Aring/ in thickness is used to separate the free layer from the bias layer resulting in low coupling fields. IrMn delivers up to 0.34 erg/cm/sup 2/ of pinning strength, resulting in stable unshielded sensor operation for device sizes below 0.2 /spl mu/m.

Study of magnetic tunnel junction read sensors

Unshielded magnetic tunnel junction (MTJ) sensors stabilized by insulating hard magnetic tails have been fabricated. Testing results showed that the control of oxidation condition was important for obtaining MTJ with low junction resistances and high TMR coefficients. The results also showed that the thickness of insulating spacer between hard magnet and MTJ stack had a significant influence on sensor stability. Finally, recording tests of stabilized MTJ read heads demonstrated linear densities of 420 Kbpi at 10/sup -9/ ontrack error.