STRUCTURAL AND MAGNETIC PROPERTIES OF NI CLUSTERS IN ALN PREPARED BY ION IMPLANTATION (invited)

Magnetic measurements performed on Ni clusters imbedded in AlN are presented. The Ni particles were prepared by ion implantation, followed by an annealing treatment. Via X-ray absorption measurements at the Ni edge, it was possible to characterize the clusters : determine the crystallographic structure and measure the lattice parameters. In a spherical assumption, average diameters, in the range 0.9 nm to 2.5 nm, are calculated. The particle size is controlled by the incident fluence and the post-annealing conditions. Depth distributions in the matrix are measured by Rutherford Backscattering of He ions. Magnetization measurements with a SQUID magnetometer show that these particles display a superparamagnetic behavior with blocking temperatures in the range 20 K to 300 K.