UC Berkeley

The absence of a Mn local moment was observed in Mn-doped amorphous silicon (a- Mnx Si1-x) films. The magnetic susceptibility obeys the Curie-Weiss law for a wide range of x (5× 10-3 up to 0.175) but with extremely small moment. Magnetization measurements suggest that this behavior occurs because only a small percentage of Mn (Mn2+ states with J=S=5/2) contribute to the magnetization. Thus, the magnetic moments are quenched for the majority of Mn atoms, contrary to the general belief of the existence of a localized Mn moment in Si. X-ray absorption spectroscopy suggests that the quenching of Mn moments is attributed to the formation of an itinerant but Anderson-localized impurity band, forming at x as low as 5× 10-3. © 2008 The American Physical Society.