Spin-flip spectroscopy in phthalocyanine based molecular magnetic tunnel junctions

Molecular spintronics is an effervescent field of research, which aims at combining spin physics and molecular nano-objects. We have investigated spin-dependent transport through metallo-phthalocyanine molecules. Cobalt phthalocyanine (CoPc) and manganese phthalocyanine (MnPc) molecules have been integrated in magnetic tunnel junctions to act as tunnel barriers. By changing only the central metal atom, very different magnetoresistance behaviours are revealed. For CoPc molecules, a tunnelling magnetoresistance (TMR) effect coexists together with a tunnelling anisotropic magnetoresistance (TAMR) [1]. For MnPc based MTJs, anisotropic MR effects dominate with no direct evidence of TMR or clear conventional TAMR effect. These differences reflect different transport mechanisms and tunnelling paths through the molecules between the electrodes. For MnPc MTJs, inelastic tunnelling with spin-flip events through the Mn atoms chain formed by the MnPc layer stacking occurs. These results show that metallo-organic molecules could be used as a template to connect magnetic atomic chains or even a single magnetic atom in a solid state device.
[1] C. Barraud et al., Phys. Rev. Lett. 114, 206603 (2015)