Interlayer exchange coupling dependence of thermal stability parameters in synthetic antiferromagnetic free layers

We conducted a detailed study of the interlayer exchange coupling (J(EX)) dependence of thermal stability properties of magnetic tunnel junctions (MTJs) with synthetic antiferromagnetic (Syn-AF) free layers. The thermal stability properties were investigated using the junction magnetoresistance of current-perpendicular MTJ devices with a word line as probes. The observed sweep-rate-dependent coercivities were analyzed using the Sharrock formula. The results confirmed the existence of strong J(EX) dependence on thermal stability parameters (KuV/kT) in Syn-AF free layers. The values of KuV/kT for MTJs with Syn-AF free layers decreased with a decrease in the strength of J(EX), and the increase in the effective volume of the Syn-AF free layer disappeared at J(EX)<= 0.52 erg/cm(2). The Syn-AF free layer with J(EX)>0.52 erg/cm(2) is relevant for high-density spin electronic nanodevices with a low aspect ratio. (C) 2006 American Institute of Physics.