Abstract
The magnetic properties of Fe ions implanted into a germanium crystal by metal-vapor vacuum arc ion source were investigated using a Quantum Design SQUID magnetometer. The presence of Fe nanoclusters in Ge was verified by magnetization measurements. A Langevin fit was used to obtain the size distribution of the clusters. The results demonstrated that the clusters are magnetic. The magnetic behavior of the clusters was characterized by zero-field-cooled and field-cooled measurements for temperatures 4.2 to 300 K. The implanted layer with magnetic clusters shows negative magnetoresistance with a positive magnetoresistance background due to the Ge substrate for parallel magnetic-field geometry at temperatures 180 to 300 K. The negative magnetoresistance is found to become dominant with decrease of temperature, The negative magnetoresistance is attributed to the existence of magnetic clusters in the implanted layer.