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arXiv · 1001.5418

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

A. Navarro-Quezada·W. Stefanowicz·Tian Li·B. Faina·M. Rovezzi·R. T. Lechner·T. Devillers·F. d'Acapito·G. Bauer·M. Sawicki·T. Dietl·A. Bonanni
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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 $T_{\mathrm{g}}$. 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 $T_{\mathrm{g}}$ (800$^{\circ}$C); ii) superparamagnetic-like -- brought about mainly by ferromagnetic nanocrystals of $\epsilon-$Fe$_3$N but also by $\gamma'$-Fe$_4$N and by inclusions of elemental $\alpha$- and $\gamma$-Fe, and prevalent in films obtained in the intermediate $T_{\mathrm{g}}$ range; iii) component linear in the magnetic field and associated with antiferromagnetic interactions -- found to originate from highly nitridated Fe$_x$N ($x \leq$ 2) phases, like $\zeta$-Fe$_2$N, and detected in samples deposited at the highest employed temperature, $T_{\mathrm{g}}$ = 950$^{\circ}$C. Furthermore, depending on $T_{\mathrm{g}}$, the Fe-rich nanocrystals segregate towards the sample surface or occupy two-dimensional planes perpendicular to the growth direction.

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A. Navarro-Quezada, W. Stefanowicz, Tian Li, B. Faina, M. Rovezzi, R. T. Lechner, T. Devillers, F. d'Acapito, G. Bauer, M. Sawicki, T. Dietl, A. Bonanni. 2010-01-29. Embedded magnetic phases in (Ga,Fe)N: the key role of growth temperature. https://doi.org/10.1103/physrevb.81.205206

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