Abstract
Extensive studies have been made on exchange bias material for their application in magneto-resistive spin-valve sensors used in high density recording. Typically, a higher degree of ordering of PtMn enhances a stronger exchange bias field of a spin valve. To understand the structure of an ordering PtMn is of importance for fabricating a good spin valve system. In this work, the relation between the exchange bias field and the in-plane structure of AF (anti-ferromagnetic) PtxMn1-x alloy was studied as functions of Mn compositions and number of annealing cycles. In-plane X-ray diffraction was used to study the in-plane ordering structures. The in-plane direction is emphasized because this direction is the same direction of the exchange field. These in-plane X-ray diffraction results show that the higher degree of chemical ordering for PtMn strongly correlated with the higher values of exchange bias field. The annealing treatment shows that the exchange bias field increases as the number of annealing cycles increase. X-ray diffraction data also show that a better ordered PtMn film was formed after annealing. However, the coherent length and the crystal orientation may play an important role in these samples. In addition, the best ordering sample is the one with Mn composition around 50%.