Unravelling the Local Crystallographic Structure of Ferromagnetic Ga$_y$Fe$_{4-y}$N Nanocrystals Embedded in GaN

Abstract

In the Fe-doped GaN phase-separated magnetic semiconductor GaδFeN, the presence of embedded γ'-Ga y 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) γ'-Ga y 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 K 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.

Magnetic Constitution of Topologically Trivial Thermoelectric PbTe:Cr

“…The recorded shape of mTRM can be quite accurately described if we assume that the whole signal is composed of two Langevin functions L(T ), that is the B J (T ) function obtained for J = ∞. This is the classical limit for the molecular field theory, which is the best approximation to describe the behavior of strong magnetic moments of individual nanocrystals [27,28,33]. These two L(T ) and their sum are marked by black dotted and dashed lines, respectively, in Fig.…”