Observation of a novel ferromagnetic phase of Ho3+in Ho/Lu superlattices

Abstract
The magnetic structures of three Ho/Lu superlattices have been investigated using neutron diffraction. The low-temperature magnetic structure adopted by the Ho3+ moments is found to depend on the number nHo of atomic planes in a single block of Ho. For a sample with nH0 approximately=40 the moments form a basal-plane spiral down to the lowest temperatures investigated, whereas for two samples with nHo3+ moments within a single block align ferromagnetically.