Researchers from the UK's Manchester University have explored opportunities presented by hexagonal boron nitride (hBN) as a prototypical high-quality two-dimensional insulator that can be used both as a barrier in MTJs and as for spin injection in lateral spin valves.
The research revealed the effect of point defects inevitably present in mechanically exfoliated hBN on the tunnel magnetoresistance of Co-hBN-NiFe MTJs. In particular, the researchers observe a marked enhancement of the magnetoresistance of the junction at well-defined bias voltages, indicating resonant tunneling through magnetic or 'spin-polarized' defect states.
These results provided the first evidence that, in devices made using standard technology (thermally evaporated electrodes) the role of localized states in hBN is determined by proximity-induced spin splitting from the adjacent ferromagnetic electrodes, rather than the usually assumed spin filter effects.
The study shows the potential of using atomically thin hBN barriers with defects to engineer the magnetoresistance of MTJs, opening the door towards exploiting the spin degree of freedom in current studies of point defects as quantum emitters.