Influence of buffer layer texture on magnetic and electrical properties of IrMn spin valve magnetic tunnel junctions

Abstract

Spin valve magnetic tunnel junctions (SV-MTJs) with the structure Si(100)∕SiOx∕buffer(A,B)∕IrMn∕CoFe∕AlOx∕NiFe∕Ta have been deposited on two buffers: Cu (group A) and Ta∕Cu (group B). The A junctions were characterized by a low degree of texture and a small amplitude of roughness, and B junctions by a high degree of texture and a high amplitude of roughness. The strongly textured buffer Ta∕Cu (group B) grew in a columnarlike fashion and induced interfacial roughness. The texture and the roughness modified strongly the interlayer and the exchange bias coupling fields in the SV-MTJs. A substantial influence of the roughness, due to barrier thickness fluctuation, on the resistance area product (R×A) of junctions was also observed. The influence on the temperature dependence of conductance and tunnel magnetoresistance (TMR) was, however, small and only observable at low temperature for the two groups of junctions. A significantly larger increase of the conductance and decrease of the TMR with increasing bias voltage was found for the A junctions. The obtained results imply that composition of buffer layers and their sequence can be used as one of the ways to improve the magnetic and tunneling properties of SV-MTJs.