TbPc2 (Terbium-Phthalocyanino) SMM • Double Decker • Structure • Electronic config. • of Tb: [Xe]4f96s2 Phthalocyanine C32H18N8
Experimental Setup • Easy axis of Ni: • Out of Plane (OP) of Ni film • and collinear with TbPc2 axis. • OP axis is created by adding • 13 monolayers of Ni on • Cu(100) surface. • Easy axis of Ni: • In Plane (IP) of Ni film and • perpendicular to TbPc2 axis. • 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 (=0o ) and grazing (=70o ) 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. • Coupling between MTb and MNi • is anti-ferromagnetic. • When easy axis of Tb is orthogonal • to Ni, Tb XMCD reduced, signaling • weakening of Tb magnetization.
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) B(T) (=70o ) (=0o )
(=0o ) (=70o )
Conclusion • SMMs couple to ferromagnetic (FM) metal film. • The superexchange interaction mediating the coupling can be tuned • by oxidizing or reducing the FM substrate. • The SMMs magnetization depends critically on the alignment of the • molecule and substrate easy axis. • The enhanced thermal stability of the TbPc2 magnetic moment and • possibility to orient it parallel or antiparallel to the substrate make • TbPc2 very interesting for application as spin valve device.