Embedded magnetic phases in (Ga,Fe)N: the 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 \(T_{\mathrm{g}}\). 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.