Influence of growth morphology on the Neel temperature of CrRu thin films and heterostructures

摘要

Dimensionality effects on epitaxial and polycrystalline Cr_(1-x)Ru_x alloy thin films and in Cr/Cr-Ru heterostructures are reported. X-ray analysis on Cr_(0.9965)Ru_(0.0035) epitaxial films indicates an increase in the coherence length in growth directions (10 0) and (110) with increasing thickness (d), in the range 2050nm, resulting in the formation of columnar structures. The Neel temperatures (T_N) of the Cr_(0.9965)Ru_(0.0035) films show anomalous behaviour as a function of d at thickness d≈50nm. It is interesting to note that this thickness corresponds to that for which a change in film morphology occurs. Experiments on epitaxial Cr_(1-x)Ru_x thin films, with 0≤x≤0.013 and d = 50nm, give T_N-x curves that correspond well with that of bulk Cr_(1-x)Ru_x alloys. Studies on Cr/Cr_(0.9965)Ru_(0.0035) superlattices prepared on MgO(100), with the Cr layer thickness varied between 10 and 50 nm, keeping the Cr_(0.9965)Ru_(0.0035) thickness constant at 10 nm, indicate a sharp decrease in T_N as the Cr separation layers reaches a thickness of 30 nm; ascribed to spin density wave pinning in the Cr layers for d<30nm by the adjacent CrRu layers.