Embedded magnetic phases in (Ga,Fe)N: Key role of growth temperature

作者：Navarro Quezada A^*; Stefanowicz W; Li Tian; Faina B; Rovezzi M; Lechner R T; Devillers T; d'Acapito F; Bauer G; Sawicki M; Dietl T; Bonanni A

来源：Physical Review B, 2010, 81(20): 205206.

DOI：10.1103/PhysRevB.81.205206

The local chemistry, structure, and magnetism of (Ga,Fe)N nanocomposites grown by metal-organic vapor-phase epitaxy are studied by synchrotron x-ray diffraction and absorption, high-resolution transmission electron microscopy, and superconducting quantum interference device magnetometry as a function of the growth temperature T(g). Three contributions to the magnetization are identified: (i) paramagnetic-originating from dilute and noninteracting Fe(3+) ions substitutional of Ga and dominating in layers obtained at the lowest considered T(g) (800 degrees C); (ii) superparamagneticlike-brought about mainly by ferromagnetic nanocrystals of epsilon-Fe(3)N but also by gamma'-Fe(4)N and by inclusions of elemental alpha-Fe, and prevalent in films obtained in the intermediate T(g) range; (iii) component linear in the magnetic field and associated with antiferromagnetic interactions-found to originate from highly nitridated Fe(x)N (x <= 2) phases, like zeta-Fe(2)N, and detected in samples deposited at the highest employed temperature, T(g)=950 degrees C. Furthermore, depending on T(g), the Fe-rich nanocrystals segregate toward the sample surface or occupy two-dimensional planes perpendicular to the growth direction.

• 出版日期2010-5-15