Paramagnetic GaN:Fe and ferromagnetic (Ga,Fe)N - relation between structural, electronic, and magnetic properties

Abstract

We report on the metalorganic chemical vapor deposition (MOCVD) of GaN:Fe and (Ga,Fe)N layers on c-sapphire substrates and their thorough characterization via high-resolution x-ray diffraction (HRXRD), transmission electron microscopy (TEM), spatially-resolved energy dispersive X-ray spectroscopy (EDS), secondary-ion mass spectroscopy (SIMS), photoluminescence (PL), Hall-effect, electron-paramagnetic resonance (EPR), and magnetometry employing a superconducting quantum interference device (SQUID). A combination of TEM and EDS reveals the presence of coherent nanocrystals presumably FexN with the composition and lattice parameter imposed by the host. From both TEM and SIMS studies, it is stated that the density of nanocrystals and, thus the Fe concentration increases towards the surface. In layers with iron content x<0.4% the presence of ferromagnetic signatures, such as magnetization hysteresis and spontaneous magnetization, have been detected. We link the presence of ferromagnetic signatures to the formation of Fe-rich nanocrystals, as evidenced by TEM and EDS studies. This interpretation is supported by magnetization measurements after cooling in- and without an external magnetic field, pointing to superparamagnetic properties of the system. It is argued that the high temperature ferromagnetic response due to spinodal decomposition into regions with small and large concentration of the magnetic component is a generic property of diluted magnetic semiconductors and diluted magnetic oxides showing high apparent Curie temperature.

21 pages, 30 figures, submitted to Phys. Rev. B

References in corpus (4)

• Ferromagnetism in substituted zinc oxide
• Electronic structure and magnetism of Mn doped GaN
• Structural, Magnetic and Electronic Properties of Fe/Au Monatomic Multilayers
• Magnetic properties of 3d-impurities substituted in GaAs

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• Experimental probing of exchange interactions between localized spins in the dilute magnetic insulator (Ga,Mn)N
• Aggregation and magnetism of Cr, Mn, and Fe cations in GaN
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• Homogenous and heterogeneous magnetism in (Zn,Co)O
• Embedded magnetic phases in (Ga,Fe)N: the key role of growth temperature
• Local structure of (Ga,Fe)N and (Ga,Fe)N:Si investigated by x-ray absorption fine structure spectroscopy
• Stretching magnetism with an electric field in a nitride semiconductor
• Fermi level and bands offsets determination in insulating (Ga,Mn)N/GaN structures
• Impact of substrate temperature on magnetic properties of plasma-assisted molecular beam epitaxy grown (Ga,Mn)N
• The Fe-Mg interplay and the effect of deposition mode in (Ga,Fe)N doped with Mg
• Out-of-Plane Magnetic Anisotropy in Ordered Ensembles of Fe${}_y$N Nanocrystals Embedded in GaN
• Planar arrays of magnetic nanocrystals embedded in GaN
• Element specific characterization of heterogeneous magnetism in (Ga,Fe)N films
• Magnetotransport in phase-separated (Ga,Fe)N with $\gamma$'-Ga${}_y$Fe${}_{4-y}$N nanocrystals
• A Simplified Method of the Assessment of Magnetic Anisotropy of Commonly Used Sapphire Substrates in SQUID Magnetometers
• Electrical characteristics of vertical-geometry Schottky junction to magnetic insulator (Ga,Mn)N heteroepitaxially grown on sapphire
• Relation between exciton splittings, magnetic circular dichroism, and magnetization in wurtzite (Ga,Fe)N
• Electronic structure of Ga${}_{1-x}$Cr${}_x$N and Si-doping effects studied by photoemission and X-ray absorption spectroscopy
• Reliable Magnetometry for Antiferromagnets and Thin Films: Correcting Substrate Artifacts in Mn3Sn/MgO Systems
• From narrow-gap and semimagnetic semiconductors to spintronics and topological matter: a life with spins