Evolution of the interfacial perpendicular magnetic anisotropy constant of the Co2FeAl/MgO interface upon annealing

Conca A, Niesen A, Reiss G, Hillebrands B. Evolution of the interfacial perpendicular magnetic anisotropy constant of the Co2FeAl/MgO interface upon annealing. JOURNAL OF PHYSICS D-APPLIED PHYSICS. 2018;51(16): 6.We investigate a series of films with different thickness of the Heusler alloy Co2FeAl in order to study the effect of annealing on the interface with a MgO layer and on the bulk magnetic properties. Our results reveal that while the perpendicular interface anisotropy constant K-S(perpendicular to) is zero for the as-deposited samples, its value increases with annealing up to a value of 1.14 +/- 0.07 mJ m(-2) for the series annealed at 320 degrees C and of 2.01 +/- 0.7 mJ m(-2) for the 450 degrees C annealed series owing to a strong modification of the interface during the thermal treatment. This large value ensures a stabilization of a perpendicular magnetization orientation for an extrapolated thickness below 1.7 nm. The data additionally shows that the in-plane biaxial anisotropy constant has a different evolution with thickness in as-deposited and annealed systems. The Gilbert damping parameter a shows minima for all series for a thickness of 40 nm and an absolute minimum value of 2.8 +/- 0.1 x 10(-3). The thickness dependence is explained in terms of an inhomogeneous magnetization state generated by the interplay between the different anisotropies of the system and by the crystalline disorder