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

Abstract

The local chemistry, structure, and magnetism of (Ga,Fe)N nanocomposites grown by metal organic vapor phase epitaxy is studied by high resolution synchrotron x-ray diffraction and absorption, transmission electron microscopy, and superconducting quantum interference device magnetometry as a function of the growth temperature Tg. Three contributions to the magnetization are identified: i) paramagnetic -originating from dilute and non-interacting Fe 3+ ions substitutional of Ga, and dominating in layers obtained at the lowest considered Tg (800 • C); ii) superparamagnetic-like -brought about mainly by ferromagnetic nanocrystals of ε−Fe3N but also by γ ′ -Fe4N and by inclusions of elemental α-and γ-Fe, and prevalent in films obtained in the intermediate Tg range; iii) component linear in the magnetic field and associated with antiferromagnetic interactions -found to originate from highly nitridated FexN (x ≤ 2) phases, like ζ-Fe2N, and detected in samples deposited at the highest employed temperature, Tg = 950 • C. Furthermore, depending on Tg, the Fe-rich nanocrystals segregate towards the sample surface or occupy two-dimensional planes perpendicular to the growth direction.

Fe dopant in ZnO: 2+ versus 3+ valency and ion-carrier s,p−d exchange interaction

“…A careful analysis of the data reveals the absence of ferromagnetic secondary phases (e.g., Fe-rich aggregates) in all of the studied samples. This is in contrast to what was reported previously for the (Zn,Fe)O 93 and other Fe-doped wide band gap semiconductors, e.g., for (Ga,Fe)N. 94,95 Consequently, the term C in the Eq. 5 will be neglected.…”

Element Specific Magnetometry Combining X-ray Circular with Linear Dichroism: Fundamentals and Applications

“…As one here probes only the polar angle, it is sucient for the specic GaN sample to be c-axis oriented. Also LEED spots were observed in this case, conrming this result in agreement to other observations for the specic sample [44]. This eect can be easily described mathematically for 2p states in a localized picture of the electronic states, forming molecular orbitals in a molecule [46].…”

Characterization of Fe-N nanocrystals and nitrogen–containing inclusions in (Ga,Fe)N thin films using transmission electron microscopy

“…The deposition process, the structure of the layers and their magnetic properties are described in detail elsewhere. 24 (Ga,Fe)N layers that were grown at 800 °C showed no evidence of secondary phases. Here, we focus on layers that were grown either at 850 °C or at higher temperatures and contain Fe-N precipitates.…”