Abstract
In the Fe-doped GaN phase-separated magnetic semiconductor Gadelta FeN, the presence of embedded gamma '-hbox {Ga}_y hbox {Fe}_{4-y}N nanocrystals determines the magnetic properties of the system. Here, through a combination of anomalous X-ray diffraction and diffraction anomalous fine structure, the local structure of Ga in self-assembled face-centered cubic (fcc) gamma '-hbox {Ga}_y hbox {Fe}_{4-y}N nanocrystals embedded in wurtzite GaN thin layers is investigated in order to shed light onto the correlation between fabrication parameters, local structural arrangement and overall magnetic properties of the material system. It is found, that by adjusting the growth parameters and thus, the crystallographic surroundings, the Ga atoms can be induced to incorporate into 3c positions at the faces of the fcc crystal lattice, reaching a maximum occupancy of 30%. The magnetic response of the embedded nanocrystals is ferromagnetic with Curie temperature increasing from 450 to 500 K with the Ga occupation. These results demonstrate the outstanding potential of the employed experimental protocol for unravelling the local structure of magnetic multi-phase systems, even when embedded in a matrix containing the same element under investigation.
Highlights
The incorporation of Fe ions into the technologically relevant GaN fabricated by metal-organic vapour phase epitaxy above a concentration of 0.4% cations leads to the self-assembly of embedded Fey N nanocrystals (NCs) with either ferromagnetic or antiferromagnetic properties imposed by the growth conditions and by the actual incorporation of the magnetic ions into the wurtzite lattice[1,2,3,4,5,6,7,8,9,10,11]
Through a combination of anomalous X-ray diffraction (AXD) and diffraction anomalous fine structure (DAFS)[24,25,26], the local-structure of self-assembled γ ′-GayFe4−y N nanocrystals embedded in GaN thin layers is investigated, in order to shed light onto the correlation between fabrication parameters, local crystallographic arrangement and overall magnetic properties of the material system
The present results demonstrate the outstanding potential of the DAFS method for unravelling the local structure of similar magnetic phase-separated systems even when the NCs and the surrounding matrix contain the same absorber under investigation, though in a different crystallographic landscape
Summary
The incorporation of Fe ions into the technologically relevant GaN fabricated by metal-organic vapour phase epitaxy above a concentration of 0.4% cations leads to the self-assembly of embedded Fey N nanocrystals (NCs) with either ferromagnetic or antiferromagnetic properties imposed by the growth conditions and by the actual incorporation of the magnetic ions into the wurtzite lattice[1,2,3,4,5,6,7,8,9,10,11]. Through a combination of anomalous X-ray diffraction (AXD) and diffraction anomalous fine structure (DAFS)[24,25,26], the local-structure of self-assembled γ ′-GayFe4−y N nanocrystals embedded in GaN thin layers is investigated, in order to shed light onto the correlation between fabrication parameters, local crystallographic arrangement and overall magnetic properties of the material system It is found, that due to the conditions imposed by the growth parameters and by the resulting crystallographic environment, the Ga atoms tend to occupy the 3c sites of the fcc structure, while the magnetic characteristics of the NCs—magnetization and Curie temperature (T C)—display an inverse correlation with the amount of Ga atoms occupying 3c sites in the NCs. The present results demonstrate the outstanding potential of the DAFS method for unravelling the local structure of similar magnetic phase-separated systems even when the NCs and the surrounding matrix contain the same absorber under investigation, though in a different crystallographic landscape
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