Structure and Magnetism of Co/Dy Superlattices
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Structure and Magnetism of Co/Dy Superlattices M. V. Makarovaa, b, E. A. Kravtsova, b, *, V. V. Proglyadoa, Yu. Khaydukovc, d, and V. V. Ustinova, b a Mikheev
b
Institute of Metal Physics, Ural Branch, Russian Academy of Sciences, Yekaterinburg, Russia Ural Federal University Named after the First President of Russia B. N. Yeltsin, Yekaterinburg, 620002 Russia c Max Planck Institute for Solid State Physics, Stuttgart, 70569 Germany d Max Planck Society Outstation at Heinz Maier–Leibnitz Zentrum, Garching, Germany *e-mail: [email protected] Received March 26, 2020; revised March 26, 2020; accepted April 2, 2020
Abstract—The effect of structural properties on the formation of the perpendicular magnetic anisotropy in Co/Dy superlattices has been studied. The superlattices are found to be composition-modulated alloys in which, on the one hand, a rigid periodicity in thicknesses and compositions takes place and, on the other hand, the interdiffusion of Co and Dy at interlayer boundaries leads to a periodic change in the Co and Dy concentrations with depth. The perpendicular magnetic anisotropy in Co/Dy is shown to be due to the perpendicular orientation of the magnetization in CoDy alloy layers, while the magnetization of Co layers is oriented in the sample plane. Keywords: metallic magnetic superlattices, interlayer magnetic ordering, perpendicular magnetic anisotropy, polarized neutron reflectometry DOI: 10.1134/S1063783420090188
1. INTRODUCTION Multilayer nanostructures formed by alternating layers of magnetic rare-earth and transition metals (REM/TM) are popular objects of studies in modern spintronics, which are characterized by the manifestation of a number of unique magnetic properties. First, because magnetic moments of heavy REM and TM are ordered antiparallelly, and the Curie temperature and magnetic moments of these metals are different, the magnetic ordering in such systems can be changed, including the compensation of magnetic moments of REM and TM sublattices, by varying the layer thicknesses and temperatures. Second, in REM/TM nanostructures with comparatively thin layers, a perpendicular magnetic anisotropy (PMA) can exist. The magnetic nanostructures, in which the magnetic compensation can be reached and PMA takes place, are widely required in various devices of magnetic spintronics, for example, in magnetooptical and thermal systems of recording and storing information with ultrafast magnetization switching, nanooscillators, etc. The first REM/TM superlattices, in which PMA was observed in fairly thick layers (to 18 Å) were the Co/Dy systems [1–3]. Recently we show that PMA can be observed in Co/Dy superlattices also at thicker Co and Dy layers (to 30 Å) in the dependence on the microstructure of the samples [4]. In this work, we study the influence of the crystal structure on the magnetic anisotropy and magnetic ordering of Co/Dy superlattices with different thicknesses of Co layers.
2. EXPERIMENTAL We studied two superlattices [Co(12 Å)/Dy(12 Å)]40 and [Co(30 Å)/Dy(12 Å)]40 grown by high
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