Spin Physics in Antiferromagnetic Metal – Molecular Interfaces

The aim of this proposal is to study the magnetic (spin) state at an antiferromagnetic metal/molecular interface. In previous experiments at ALBA, we observed that the Mn-L2,3 absorption edges of PtMn films show an enhanced x-ray magnetic circular dichroism (XMCD) signal and paramagnetic dependence with field at 290 K when a C60 layer is grown on top. This seems to correlate with a factor 3-5 higher Spin Hall Magnetoresistance (SHMR) in Y3Fe5O12/PtMn/C60 compared to Y3Fe5O12/PtMn samples without the molecular overlayer. Below ~50 K, PtMn films undergo an antiferromagnetic (AFM) transition, changing the sign of the SHMR and giving rise to an exchange bias in field-cooled adjacent magnetic layers. The C60 overlayer increases the SHMR below ~30 K in PtMn films with thickness ≥2 nm, but maintains a positive SHMR for PtMn layers ≤1.5 nm. Here, we propose soft x-ray absorption spectroscopy (XAS) and XMCD experiments at the Mn-L2,3 and C-K absorption edges to unravel the effect of C60 on the spin states of the metal-molecular interface above and below the Néel temperature (TN ~ 50 K), which can enable the use of molecular layers to tune exchange interactions and spin transport in antiferromagnets.