Coupling Single Molecule Magnets to Ferromagnetic Substrates Tb

Coupling Single Molecule Magnets to Ferromagnetic Substrates

Tb. Pc 2 (Terbium-Phthalocyanino) SMM q Double Decker Structure q Electronic config. of Tb: [Xe]4 f 96 s 2 Phthalocyanine C 32 H 18 N 8

Experimental Setup Easy axis of Ni: ØOut of Plane (OP) of Ni film and collinear with Tb. Pc 2 axis. Easy axis of Ni: ØIn Plane (IP) of Ni film and perpendicular to Tb. Pc 2 axis. ØOP axis is created by adding 13 monolayers of Ni on Cu(100) surface. Ø IP axis is created by adding 6 monolayers of Ni on Ag(100) surface. A magnetic field B was applied parallel to x-ray direction at normal ( =0 o ) and grazing ( =70 o ) incidence to measure OP and IP magnetization.

X-ray Magnetic Circular Dichcroism (XMCD): Difference spectrum of two x-ray absorption spectra (XAS) taken in a magnetic field, one taken with left circularly polarized light, and one with right circularly polarized light. q Coupling between MTb and MNi is anti-ferromagnetic. q When easy axis of Tb is orthogonal to Ni, Tb XMCD reduced, signaling weakening of Tb magnetization.

X-ray Absorption spectra (XAS)

Tuning Exchange Interaction Addition of a oxygen layer between Pc and Ni film results in oxidation of Pc ligand. Exchange field ~ 0. 6 T Doping of Ni film with Li leads to reduction of Pc ligand. Exchange field ~ 2. 5 T B(T) ( =0 o ) B(T) ( =70 o )

Conclusion q SMMs couple to ferromagnetic (FM) metal film. q The superexchange interaction mediating the coupling can be tuned by oxidizing or reducing the FM substrate. q The SMMs magnetization depends critically on the alignment of the molecule and substrate easy axis. q The enhanced thermal stability of the Tb. Pc 2 magnetic moment and possibility to orient it parallel or antiparallel to the substrate make Tb. Pc 2 very interesting for application as spin valve device.