Effect of Spin-Glass Ordering on Conduction in a-Si1-cMnc near the Metal-Insulator Transition

• Published in: physica status solidi (b) Vol. 205; no. 1; pp. 299 - 303
• Main Authors: Yakimov, A. I., Dvurechenskii, A. V., Adkins, C. J.
• Format: Journal Article
• Language: English
• Published: Berlin WILEY-VCH Verlag 01.01.1998; WILEY‐VCH Verlag
• ISSN: 0370-1972; 1521-3951
• DOI: 10.1002/(SICI)1521-3951(199801)205:1<299::AID-PSSB299>3.0.CO;2-0

The electrical conductivity and magnetoresistance of amorphous Si films implanted by Mn ions up to a concentration of 22 at% are investigated near the metal–insulator transition (MIT). We find that there is a characteristic temperature TSG = 6 to 20 K (dependent on the Mn concentration) which separates two different conductivity behaviours. As temperature is reduced below TSG on the insulating side of the MIT, the conductivity mechanism is found to change from variable‐range hopping to conductivity with constant activation energy ΔE which decreases linearly in a magnetic field. The activation energy of hopping determined from the data above TSG, on approaching TSG, turns out to be smaller than ΔE. In the metallic regime at T < TSG, we observe a shift of the MIT towards higher impurity concentration in respect with that determined from the data at T > TSG. The low‐temperature anomalies are ascribed to the spin‐glass transition caused by d–d interaction between Mn atoms.