Size-dependent magnetic order and giant magnetoresistance in organic titanium–benzene multidecker cluster

Abstract

Using density functional theory and non-equilibrium Green's function method, we investigated the magnetic and transport properties of small organic titanium–benzene sandwich clusters Ti_nBz_n+1 (n = 1–3). The results show that TiBz₂ is nonmagnetic while Ti₂Bz₃ and Ti₃Bz₄ are ferromagnetic, and our prediction is in agreement with experimental observation. The double exchange mechanism plays a key role in the ferromagnetism of larger clusters. With Ni as the two electrodes, significant spin-filter efficiency (SFE) and giant magnetoresistance (GMR) were found in the Ti_nBz_n+1 molecular junction. These transport properties could be controlled by cluster size, bias voltage or gate voltage. Specially, a sign-reversible GMR effect was observed in the Ti₂Bz₃ molecular junction. Finally, the microscopic mechanisms of SFE and GMR were suggested.