The authors report the transport properties of ferromagnetic Ga0.97 Cr0.03 N films with a Curie temperature of over 900 K. Samples synthesized under conditions that produce the maximum occupancy of Cr atoms on the Ga site (∼90%) and the maximum ferromagnetic moment of ∼0.6 μB Cr (775 °C growth temperature) exhibit a T-14 dependence of resistivity, indicative of Mott [J. Non-Cryst. Solids 1, 1 (1968)] phonon-assisted variable range hopping between deep level defects. The observation of variable range hopping in ferromagnetic films indicates that ferromagnetism results from a double-exchange-type mechanism. Films grown at higher temperatures (>800 °C) show enhanced Cr segregation, properties associated with percolative transport, and very small, if any, ferromagnetic moments.
ASJC Scopus subject areas
- Physics and Astronomy (miscellaneous)