Enhanced exchange bias and thermal stability of magnetic tunnel junctions with Ta blocking layer

An antiferromagnetic/ferromagnetic (AFM/FM) structure with an ultra-thin Ta blocking layer was investigated in order to improve thermal stability after an annealing process. Measurements by X-ray photoelectron spectroscopy directly confirm the interdiffusion mechanism of Mn atoms of IrMn in exchange-biased structure with increasing annealing temperature. Experimental results show that Mn atoms in NiFe/IrMn structure lead to faster thermal diffusion than those in CoFe/IrMn structure. The diffusion of Mn atoms induces anomalous reduction of exchange bias strength. Finally, the insertion of an ultra-thin Ta layer between FM and AFM structure as anti-diffusion barrier effectively protects the expected Mn diffusion for annealing temperatures up to 800 .deg. C, resulting in enhancement of thermal stability.