ISSN:
1089-7550
Quelle:
AIP Digital Archive
Thema:
Physik
Notizen:
Two series of samples, Ag/56Fe/57Fe/56Fex/MnF2 and Ag/56Fe/57Fe/Agx/MnF2 with Ag and Fe in (111) and (110) orientations, respectively, have been grown epitaxially in ultrahigh vacuum (∼1×10−9 τ). Several thicknesses are chosen for the 56Fe and Ag intervening layers separating 57Fe and MnF2. The magnetic hyperfine field for the 57Fe probe layer about 3 monoatomic layers (ML) thick is measured with Mössbauer spectroscopy from room temperature down to 4.2 K. For the first series of samples, a quasi-linear temperature dependence of the hyperfine field is observed for the probe layer up to 10 ML away from the (110)Fe/MnF2 interface. The magnitude of the linear slope is smaller for the 10-ML sample than for the 5-ML sample. An ordinary T3/2 dependence is recovered when the 57Fe probe layer is placed 25 ML away from the interface. This result can be qualitatively understood within the framework of a semiclassical spin-wave calculation involving a large positive surface anisotropy constant Kss by Rado. For the second series of samples, significant amount of FeF2 (about 40% of the 57Fe) is found to be present in the 57Fe probe layer. The temperature dependence of the hyperfine field exhibits an initial weak dependence at low temperatures (〈76 K) changing over to a fast quasi-linear falloff at higher temperatures for both samples with x(Ag)=9 and 19 ML. A possible explanation for this behavior is that below ∼76 K, the Néel temperature for antiferromagnetic FeF2, the 57Fe probe behaves as a three-dimensional antiferromagnet and thus exhibits a T2 dependence, while for temperatures above ∼76 K it exhibits a quasi-linear temperature dependence presumably due to the same mechanism responsible for the quasi-linear temperature dependence in the first series of samples.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1063/1.345928
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