Paramagnetic Mn-implanted amorphous Si

Different fluences of Mn ions have been implanted into 200 nm thick, n-type conducting amorphous Si films on a cold stage cooled by liquid N2 with a Mn concentration in Mn_xSi_1-x ranging from x=0.0006 to 0.088. Magnetic measurements reveal paramagnetism in all the films at temperatures down to 2 K. The field dependent magnetization curves were well fitted by Brillouin functions, indicating that the magnetically active Mn ions are on Mn_I ²⁺ interstitial sites with J=5/2. Only a small percentage of the implanted Mn ions contribute to the magnetization, indicating that the magnetic moments are quenched for most of the Mn ions, which was attributed to the nonuniform distribution of Mn ions in amorphous Si. Positive magnetoresistance due to ordinary magnetoresistance was observed at 5 K in the highest fluence Mn implanted amorphous Si film, indicating the lack of magnetic scattering of the conducting electrons by the implanted Mn²⁺ ions.