Confirmation of room temperature ferromagnetism for Mn-doped ZnO micro-tetrapod powders

Room temperature ferromagnetism in the Mn-doped ZnO micro-sized tetrapod powders, synthesized by conventional thermal evaporation, has been confirmed by static and dynamic magnetic property measurements on a large scale of bulk composite samples. A saturation magnetization of 0.02 emu/g and a coercivity of 80 Oe were obtained. No Mn or Mn-rich cluster was detected on the tetrapods by XRD and TEM analysis. The permittivity, permeability and reflection loss spectra of the Zn(Mn)O-polymer composites with various Zn(Mn)O contents have been investigated in a wide frequency range. The ferromagnetism was assumed to originate from carrier-mediated exchange coupling in the high surface density tetrapods.