Abstract
Materials with high volume magnetization are perpetually needed for the generation of sufficiently large magnetic fields by writer pole of magnetic hard disks, especially for achieving increased areal density in storage media. In search of suitable materials combinations for this purpose, we have employed density functional theory to predict the magnetic coupling between iron and gadolinium layers separated by one to several monolayers of 3d transition metals (Sc-Zn). We demonstrate that it is possible to find ferromagnetic coupling for many of them and in particular for the early transition metals giving rise to high moment. Cr and Mn are the only elements able to produce a significant ferromagnetic coupling for thicker spacer layers. We also present experimental results on two trilayer systems Fe/Sc/Gd and Fe/Mn/Gd. From the experiments, we confirm a ferromagnetic coupling between Fe and Gd across a 3 monolayers Sc spacer or a Mn spacer thicker than 1 monolayer. In addition, we observe a peculiar dependence of Fe/Gd magnetic coupling on the Mn spacer thickness.
Highlights
High magnetic moment materials are used in several technological applications such as write heads in hard disks, generators, transformers, electrical vehicles and wind turbines[1]
We look at the single spacer layer case scanning all the 3d transition metals as interlayer between ferromagnetic transition metals d6 (Fe) and Gd layers
The electronic configuration of the spacer layer and the number of 3d electrons is crucial for the magnetic coupling apart from the induced or intrinsic magnetic moment of spacer atoms
Summary
High magnetic moment materials are used in several technological applications such as write heads in hard disks, generators, transformers, electrical vehicles and wind turbines[1]. In order to realize a material with a combination of both high spin magnetic moment and high Curie temperature, heterostructures of rare-earth-metal (e.g., Gd) and Fe with a high Curie temperature[5] intermediated by a single Cr layer was proposed theoretically and a proof of principle experimental verification was presented. It is important to note that the overcoming of the SPM by Fe/X/Gd heterostructures proposed here is by the way of enhancing the magnetic ordering temperature of Gd and is not due to the enhancement of the moments of either Fe or Gd. Among the 3d transition metals Fe, Co and Ni are ferromagnetic (FM) while Cr and Mn are antiferromagnetic (AFM) in their bulk form. It is observed that the magnetic coupling between Fe and Gd persists to thicker Mn spacer layer while the coupling is diminished for a Sc spacer above 3 monolayers (ML) thick
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