Transition-metal blends incorporated into CuO nanostructures: Tuning of room temperature spin-ferromagnetic order

Abstract

In this study, notable ferromagnetic features were realized in lightly multidoped Cu0·97Mn0·01Fe0·01Ni0·01O composition at room temperature. Variable and dilute multidoped compositions composed of CuO, Cu0·97Cr0·01Mn0·01Fe0·01O, Cu0·97Mn0·01Fe0·01Ni0·01O, and Cu0·97Mn0·01Co0·01Ni0·01O powders were fabricated via coprecipitation approach. The crystal structural analysis of the synthesized compositions indicated that a high purity mono-phase of monoclinic CuO structure was formed and also ruled out the existence of any other impurities. The Fourier-transform infrared (FT-IR) spectra demonstrated the characteristic vibrational absorption modes of CuO structure. The transmission electron microscopy (TEM) images revealed that the pure CuO has approximately nano-sized spherical particles while Cu0·97Cr0·01Mn0·01Fe0·01O, Cu0·97Mn0·01Fe0·01Ni0·01O and Cu0·97Mn0·01Co0·01Ni0·01O powders have nano-spherical particles as well as some elongated particles. Optically, the incorporation of these transition metals blends leads to formation of long absorption tails and obvious red shifts for the band gap energy of CuO. Exactly, CuO, Cu0·97Cr0·01Mn0·01Fe0·01O, Cu0·97Mn0·01Fe0·01Ni0·01O and Cu0·97Mn0·01Co0·01Ni0·01O samples exhibit infrared band gap energies of 1.42, 1.4, 1.25 and 1.2 eV, respectively. Magnetically, at room temperature Cu0·97Mn0·01Fe0·01Ni0·01O exhibits a perfect ferromagnetic performance with high saturation magnetization of 1.15 emu/g and coercivity of 76 Oe. It seems that the multidoping induced a robust ferromagnetic state via Cu2+-Mn + or Mn + -Mn + exchange interactions (M = Mn, Fe, Ni) into CuO, leading to remarkable room temperature magnetic characteristics.