Neutron diffraction study of artificial CoO-NiO superlattices

Neutron diffraction measurements were made on artificial superlattices of CoO-NiO, (CoO)m(NiO)n×l prepared on the (0001) surface of α-Al2O3. (111) layers of CoO and NiO, each less than 2 nm thick (2≤m,n≤8), were stacked alternatively to a total thickness of less than 70 nm (m+n≤15,l≤25). A well-defined magnetic Bragg peak indexed as (1/2 1/2 1/2) was observed for all the samples, and a magnetic structure of type FCC2 with the spin axis lying in the (111) planes grown was suggested. The temperature dependence of the magnetic peak intensity revealed a sharp, single magnetic transition. The Néel temperature was found to vary as a linear function of n/(m+n).