Molecular-orientation-dependent magnetic properties of iron phthalocyanine (FePc) thin films and microwires

Abstract

The development of molecular magnets plays a major role in emerging organic spintronics applications, as it exhibits both semiconducting and magnetic properties. Herein, we report on the molecular-orientation-dependent magnetic properties of iron phthalocyanine (FePc) thin films and microwires. FePc thin films grown on SiO2 and flexible kapton substrates clearly reveal that the morphology is strongly influenced by the substrates and film thickness. Meanwhile, the molecular stacking orientation of FePc thin films can be tuned by 3, 4, 9, 10-perylenetetracarboxylic dianhydride (PTCDA) templating layer and film thickness. Magnetic hysteresis loops show that the iron atoms are strongly magnetically coupled into ferromagnetic chains at low temperature with high coercivity at 1000 Oe. The magnetization and susceptibility of FePc thin films are dependent on the molecular orientation, and the Curie–Weiss constant is modulated from 24 ± 2 K K to 35 ± 2 K through the templating effect, in which the molecular stacking orientation changes from standing-up to lying-down arrangement. Furthermore, strong orientation dependent ferromagnetism is also observed in low-dimensional η-FePc microwires, in which the Curie–Weiss constants change from 20 ± 2 K to 35 ± 2 K when magnetic field rotated from short wire axis to long wire axis. The ability to fabricate FePc thin films on flexible substrate with controllable molecular orientation and ferromagnetism makes them promising candidates for flexible spintronic devices.