Unravelling the local crystallographic structure of ferromagnetic $$\gamma '$$-$$\hbox {Ga}_y \hbox {Fe}_{4-y}$$N nanocrystals embedded in GaN

Abstract

In the Fe-doped GaN phase-separated magnetic semiconductor Ga$$\delta $$ δ FeN, the presence of embedded $$\gamma '$$ γ ′ -$$\hbox {Ga}_y \hbox {Fe}_{4-y}$$ 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) $$\gamma '$$ γ ′ -$$\hbox {Ga}_y \hbox {Fe}_{4-y}$$ 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 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.

In Situ Compensation Method for Precise Integral SQUID Magnetometry of Miniscule Biological, Chemical, and Powder Specimens Requiring the Use of Capsules

“…To quantify this PM component, we measure m(H) at two very low temperatures: 1.8 and 5 K, shown in Figure 15b. Clearly, the two dependencies have a Brillouinlike character at high magnetic fields, with noticeable FM-like deviations around H = 0, similar to that at 300 K. In order to accurately separate the PM signal in our turmeric sample, we invoke the fact that in most cases it is only the PM component that is responsible for changes of m(H) at low temperatures, a condition met in many magnetically composite systems in which the technique presented below worked with a very high precision [3,[48][49][50]. The diamagnetism should not depend on T, so should most of the FM contaminations, as latter are typically characterized by a very high spin coupling temperatures.…”

In Situ Compensation Method for Precise Integral SQUID Magnetometry of Miniscule Biological, Chemical, and Pow-der Specimens Requiring the Use of Capsules

“…From the slope of this m(H), we evaluate the diamagnetic susceptibility as turmeric  −3. In order to accurately separate the PM signal in our turmeric sample, we invoke the fact that in most cases it is only the PM component that is responsible for changes of m(H) at low temperatures, a condition met in many magnetically composite systems in which the technique presented below worked with a very high precision [3,[48][49][50]. The diamagnetism should not depend on T, so should most of the FM contaminations, as latter are typically characterized by a very high spin coupling temperatures.…”