Unusual magnetic behavior in a chiral-based magnetic memory device

In recent years chiral molecules were found to act as efficient spin filters. Using a multilayer structure with chiral molecules magnetic memory was realized. Observed rare magnetic phenomena in a chiral-based magnetic memory device was reported by O-Ben Dor et. al in Nature Commun, 4, 2256 (2013). This multi-layered device is built from α-helix L-polyalanine (AHPA-L) adsorbed on gold, Al₂O₃ (7 nm) and Ni (30 nm) layers. It was shown that certain temperature range the FC branch crosses the magnetic peak (at 55 K) observed in the ZFC curve thus ZFC>FC. We show here that in another similar multi-layered material, at low applied field, the ZFC curve lies above the FC one up to 70 K. The two features have the same origin and the crucial necessary components to exhibit them are: AHPA-L and 30 nm Ni layered thick. Similar effects were also reported in sulfur doped amorphous carbon. A comparison between the two systems and the ingredients for these peculiar observations is discussed.