Signatures of enhanced ordering temperatures in digital superlattices of (LaMnO_3)_m/(SrMnO_3)_(2m)

摘要

Digital superlattices of (LaMnO_3)_m/ SrMnO_3)_(2m) (m≤ 3) having the same nominal composition as La_(1/3)Sr_(2/3)MnO_3, an antiferromagnetic insulator, have been synthesized by means of molecular beam epitaxy. All superlattices show a sharp resistive maximum at temperatures near to or higher than the Neel temperature of bulk La_(1/3)Sr_(2/3)MnO_3. No discernible signatures of magnetic ordering are observed near the resistivity peak for m≤ 2, but m=3 has a susceptibility peak consistent with antiferromagnet ordering, which is canted when cooled in a small magnetic field. Analogies are drawn to d_(x~2_y~2) orbitally ordered, layered antiferromagnetic manganites to explain the observations.