The L12 -phase formation and resultant exchange anisotropy were examined in Mn-Rh/Co-Fe and Mn-Ru/Co-Fe bilayers, varying the substrate temperature, Tsub, during the deposition of Mn-Rh or Mn-Ru layer. The superlattice diffractions from the Mn3Rh were detected. The unidirectional anisotropy constant, JK, was enhanced more than double with increasing Tsub from room temperature to 130°C ∼ 170°C, similarly to Mn-Ir/Co-Fe bilayers. The maximum JK value obtained was 0.77 erg/cm2 for the Mn-Rh/Co-Fe bilayer and 0.56 erg/cm2 for the Mn-Ru/Co-Fe bilayer. The blocking temperature, T B, was increased about 80°C to 100°C, in accordance with enhancing JK. Variations of JK and TB as a function of antiferromagnetic layer thickness, dAF, were also studied. The critical thickness of dAF was less than 5 nm for both the bilayers.
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