Preparation and Magnetic Properties of Multilayer Films Based on Self-Assembly

The preparation and magnetism of four multilayer films, (DABT/Ni 2+ /PAA) 15×2, (DABT/Cu 2+ /PAA) 15×2, (PAA/DABT) 20×2 −Ni 2+, and (PAA/DABT) 20×2 −Cu 2+, which were obtained by self-assembly of 2,2′-diamino-4,4′-bithiazole (DABT), poly(acrylic acid) (PAA), and transition metal ions (Cu 2+ or Ni 2+ ) on polyethylene (PE) substrate, were described. The driving force for building up the multilayer film was identified by infrared spectroscopy. UV−vis spectra and AFM images were applied to characterize these films and indicate the uniform assembling process. The magnetic behavior was examined as a function of magnetic field strength at 4 K and as a function of temperature (4−300 K). All films display good soft ferromagnetic properties, even affected by the diamagnetic substrate. It is found that (PAA/DABT) 20×2 −Ni 2+ exhibits a fairly high value of relative saturation magnetization ( M s = 37.3 emu/g), while (DABT/Ni 2+ /PAA) 15×2 exhibits a high Curie−Weiss temperature (θ = 242 K). The magnetic results show that different assembling processes can infect the alignment of adjacent paramagnetic spins and induce different magnetic phenomena.