Microstructural evolution and magnetic properties of size-controlled nanocrystalline Ni in Ni(OH)₂–ZrO₂ composite

Size-controlled nanocrystallites of Ni varying in size from 2 to 26 nm distributed in a nonmagnetic matrix of Ni(OH)₂–ZrO₂have been prepared by changing the reduction reaction time and by adding different concentrations of ZrOCl₂solution to the initial reaction mixture. X-ray photoelectron spectroscopy indicates the presence of B₂O₃, Ni(OH)₂, and ZrO₂with Ni nanocrystals in the as-prepared composites. The room-temperature saturation magnetization and coercivity of the composites increases from ∼1.5 to 10 emu g⁻¹and 100 to 200 Oe, respectively, when the ZrOCl₂concentration in the reaction mixture increases to 0.10 M. The nanocrystals prepared without the addition of ZrOCl₂exhibit a typical ferromagnetic response at 300 K, while that prepared with the addition of 0.10 M ZrOCl₂shows a ferromagnetic response up to 400 K with higher saturation magnetization and coercivity.