Study of annealing and exchange bias effects in PtMn based magnetic tunnel junction system

Abstract

The crystallization structure and thickness of PtMn layer in a magnetic tunnel junction system are important factors to improve its exchange bias effect. This study shows that the PtMn layer could be changed from a FCC (111) structure to a FCT (111) structure after annealing above 270 °C. The minimum thickness of PtMn layer is found to be 10 nm for exchange coupling effect to be occurred in our MTJ system. The magnetic exchange effect between PtMn and SAF layers is near 4,300 Oe. Annealing temperatures can be higher than 400 °C for samples without patterning; however, temperature at 275 °C is too high for samples after patterning. This may be due to the breakdown of edges of the patterned samples as well as the complicated environments around the patterned samples.

High-temperature magnetoresistance study of a magnetic tunnel junction

“…1. The crystallization of the PtMn layer was studied below 400 1C, and the MR ratio and exchange field were found to be closely related to the phase change of the structure of PtMn [10]. The samples were measured at a constant bias of 50mV with varying temperatures between 25 and 140 1C.…”

Composition dependence of exchange anisotropy in Pt x Mn1−x /Co70Fe30 films

“…1(b) for comparison with a small arrow on the vertical axis. 2,30) Nevertheless, to prove the transformation from the FCC phase to the FCT phase for PtMn, we performed an in-plane XRD that is shown in Fig. 3.…”

“…For the FCC-Pt x Mn 1−x samples, the J K value shows a peak of 0.15 erg cm −2 at around x = 15 at%, which is larger than in other reports. [28][29][30][31][32][33][34] In addition, by decreasing the Pt content from x = 15 at%, the EB decreases and disappears at around x = 10 at%. For the FCT-Pt x Mn 1−x samples, the J K value shows a peak of 0.20 erg cm −2 at around x = 48 at%.…”