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

We conducted a detailed comparative study of thermal stability properties over a thermal excitation of switching of the free layer in a magnetic tunnel junction (MTJ) with Ni ₈₁Fe ₁₉, Co ₉₀Fe ₁₀, and synthetic antiferromagnetic (Syn-AF) free layers with several strengths of interlayer exchange coupling (J _EX). 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 strong J _EX dependence on thermal stability parameters ( K _u V / kT ) in Syn-AF free layers. The values of K _u V / k _B T 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 {less-than or slanted equal to} 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.