Quenched magnetic moment in Mn-doped amorphous Si (\textit{a}-Mn$_{x}$Si$_{1-x}$) across the metal-insulator transition

Abstract

The magnetic and electrical transport properties of Mn-doped amorphous silicon (a-Mn x Si 1−x ) thin films have been measured. The magnetic susceptibility obeys the Curie-Weiss law for a wide range of x (0.005-0.175) and the saturation moment is small. While all Mn atoms contribute to the electrical transport, only a small fraction (interstitial Mn 2+ states with J=S=5/2) contribute to the magnetization. The majority of the Mn atoms do not possess any magnetic moment, contrary to what is predicted by the Ludwig-Woodbury model for Mn in crystalline silicon. Unlike a-Gd x Si 1−x films which have an enormous negative magnetoresistance, a-Mn x Si 1−x films have only a small positive magnetoresistance, which can be understood by this quenching of the Mn moment.