Spin transport in ferrimagnetic LaCrO3/LaMnO3 superlattices*

Understanding the fundamental mechanisms which govern and enhance spin transport in materials is technological and scientific interest due to potential applications in novel spintronic devices and quantum computation. While spin transport in normal metals has been explored extensively, open questions remain related to the spin transport properties of antiferromagnetic and ferrimagnetic systems. Here, we studied the temperature-dependent spin coherence length in ferrimagnetic LaCrO₃/LaMnO₃(LCO/LMO) superlattices. The antiferromagnetic Mn-Cr coupling in LCO/LMO superlattices confirmed by X-ray circular dichroism measurements leads to a paramagnetic to ferrimagnetic transition at 100 K. Changes to the spin coherence length in the paramagnetic (above T_C) and ferrimagnetic  (below T_C) phases are investigated by ferromagnetic resonance (FMR) spin pumping measurements. Here, ferromagnetic LaSrMnO₃ or nickel alloy layers serve as the spin source/sink and are deposited adjacent to the epitaxially grown LCO/LMO superlattices. The spin coherence length of LCO/LMO system are derived from the frequency-dependence of the FMR response above and below the magnetic phase transition. By tuning the period and thickness of the LCO/LMO superlattices with atomic-scale control using the molecular beam epitaxy, we demonstrate effective pathways for modulating spin transport in artificially layered systems.