Iron Clustering and the Magnetic Properties in α-Al 2 O 3 Crystals after Iron Implantation to High Doses

Abstract

Magnetization and magnetoresistance were studied in iron-ion-implanted aluminum oxide crystals. The implantation was done up to a total dose of 3.5 x 1017 ions/cm2 into Al2O3 substrates with projectile energy of 100 keV. Using conversion electron Mossbauer spectroscopy, it is shown that most of the implanted ions precipitate as α-Fe clusters and that the nano-size clusters exhibit a transition from superparamagnetic to ferromagnetic state at the dose range of (1.5–2.0) x 1017 ions/cm2. A maximum magnetoresistance ratio of 7.5% was observed around a dose of 1.5 x 1017 ions/cm2 at a field of H=1.2 T.