Thermal stability of spin valves incorporating new amorphous ZrAl alloy films as under and capping layers

We investigated the thermal stability and interdiffusion behavior of new amorphous ZrAl-based spin valves (SVs) and compared them with similarly structured Ta-based top (T) and bottom (B) SVs. The magneto-resistance (MR) ratios of ZrAlbased T-and B-SVs were enhanced from 8.49 to 9.14% and from 6.91 to 7.54%, respectively. The Ta-based SVs degraded relatively quickly at elevated temperatures because of interlayer diffusion. In contrast, the MR ratio of the ZrAl-based T-SV decreased by only 6.6% (9.14 → 8.54%), while that of the B-SV increased by 2.3% (7.54 → 7.71 %), after annealing at 300°C for 240 min. This result and the Auger electron spectroscopy (AES) depth profile clearly showed that ZrAl-based SVs have high interdiffusion resistance. Transmission electron microscopy (TEM) and atomic force microscopy (AFM) analyses of the root-mean-square (rms) roughness indicated that the ZrAl layer (0.162 nm) has a smoother interface than the Ta layer (0.431 nm). The ZrAl-based SV has a fine, dense microstructure. It resists interdiffusion at elevated temperature and results in superior thermal stability over traditional Ta-based SVs.