Abstract
Topologically stable spin spiral structures in rare-earth (RE) can form the basis of realizing all-spin-based technology as strong exchange coupling has been reported earlier at the ferromagnet (FM)–RE or RE–RE interfaces around the temperature range where both layers are essentially ferromagnetic. Owing to the small number of irreversible spins in the non-collinear configuration within the RE layer, very weak coupling is rendered around the temperature range of the helical phase. Competing anisotropies in Er result in a conical c-axis ferromagnetic structure below 20 K while Tb orders ferromagnetically with an easy axis along the a-axis below 221 K. Here, we grow heteroepitaxial Er/Tb multilayers and find an exchange coupling of up to +170±10 Oe, particularly below 20 K. This exchange bias phenomenon can be due to the effect of spin spiral to conical phase fraction within Er below 20 K. Additionally, we find inter-domain magnetic AC frequency-responsive magnetic interaction behavior which does not comply with the spin-freezing/blocking like ordering around the crossover range of helical to conical phase. Empirically, this can be explained in terms of the increased spin-imbalance in each Er magnetic sublattice due to the atomic disorder induced during the field cooling process. This unconventional exchange coupling could essentially enable us to tailor non-collinear spintronic devices in the future with induced spin-imbalance in the RE sublattice.
Published Version
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