ISSN:
1089-7550
Source:
AIP Digital Archive
Topics:
Physics
Notes:
Ho/Y and Ho/Er superlattices have been grown by molecular-beam epitaxy using a Balzers UMS 630 instrument. The superlattices were grown on a sapphire substrate with an Nb buffer and Y seed layer. X-ray-diffraction techniques were used to characterize the crystallographic structure and neutron-diffraction techniques to determine the magnetic structures. The results for the Ho/Y systems were consistent with long-range order being formed coherently through the whole superlattice. The moments in the Ho layers were aligned in the basal plane and most of the structures could be described by helical structures with a turn angle between holmium planes of ΨH and between nonmagnetic Y planes ΨY. ΨY is found to be largely independent of temperature or superlattice, while ΨH decreases with decreasing temperatures and at low temperatures takes a commensurate value, so as to take advantage of the basal plane anisotropy. The results for the Ho/Er superlattices differ because the Er has a magnetic moment and the anisotropy favors alignment along the c axis. Between the ordering temperature of bulk Ho and bulk Er, the results are similar to those of the Ho/Y superlattices. The ordering propagates through the Er layers but the Er moments are not ordered. At lower temperatures the Er moments order in a cycloidal (a/c) structure with the basal plane components having fairly long-range coherence with the Ho moments, but the c-axis components having no coherence from one Er layer to the next.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.358303
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