Magnetic nano-particles of Ni in MgO single crystals by ion implantation

Magnetic Ni nano-particles in the near surface regions of MgO single crystals have been synthesized by 64 keV Ni ion implantation to 1 X 10(17) cm(-2) followed by thermal annealing. Transmission electron microscopy (TEM) and magnetic properties measurement system (MPMS) equipped with a superconducting quantum interference device (SQUID) detector have been employed to characterize the microstructure and magnetic properties of the Ni nano-particles. The average particle size ranges 3-5 nm in the as-implanted sample and 8-10 nm in the annealed sample. The orientation of Ni particles is perfectly matched with that of the MgO matrix. The M-H hysteresis loop measured at 10 K revealed the coercivity, H-c, similar to 195 Oe. The superparamagnetism of Ni particles was evident in as-implanted sample at the temperature above 35 K but did not show in the annealed sample. (c) 2005 Elsevier B.V. All rights reserved.