Structural and magnetic properties of $\lbrack$Er|Tb$\rbrack$multilayers

Abstract

We have investigated the structural and magnetic properties of (Er|Tb) multilayers by different scattering methods. Diffuse X-ray scattering under grazing incidence reveals the interface structure in (Er|Tb) bilayers and trilayers, indicating vertically correlated roughness between the Er and Tb interfaces. The magnetic properties of (ErnEr |TbnTb ) superlattices have been studied as a function of the superlattice composition (indices denote the number of atomic layers). Coupled ferromagnetic structures exist in all investigated samples. The phase transition temperature varies with the Tb layer thickness. Modulated magnetic order is short range for all samples beside the (Er20|Tb5) superlattice, the sample with the smallest Tb layer thickness. We observe dipolar antiferromagnetic coupling between single ferromagnetic Tb layers in all samples, with the onset of this ordering depending on the Tb layer thickness. Due to competing interactions, exchange coupling is limited to the interface near region. Therefore long range modulated magnetic order is observed in the (Er20|Tb5) superlattice only, where the interface regions overlap. The distinct differences to the magnetic structure of an Er0.8Tb0.2 alloy film are explained by a highly anisotropic arrangement of neighbouring atoms due to the correlated roughness. PACS. 75.75.+a Magnetic properties of nanostructures - 75.25.+z Spin arrangements in magnetically ordered materials (including neutron and spin-polarized electron studies, synchrotron-source X-ray scattering, etc.) - 61.18.Fs Magnetic resonance techniques; Mossbauer spectroscopy