Anomalous second ferromagnetic phase transition as a signature of spinodal decomposition in Fe-doped GeTe diluted magnetic semiconductor

Abstract

Structural and magnetic properties of diluted magnetic semiconductor Ge1-xFexTe thin films are investigated. The conventional structure analysis shows c-axis orientation with columnar growth of the films and no indication of Fe clusters or second phase. Magnetic measurements combined with theory models reveal that two ferromagnetic phase transitions occur. We consider that the second ferromagnetic phase transition in high Fe content thin film is from a ferromagnetic phase with long range exchange interaction to a superparamagnetic phase with dipole interaction between Fe clusters, which can be viewed as a signature of spinodal decomposition in Ge1-xFexTe material.

Magnetic-field-tuned charge density wave in SmNiC2and NdNiC2

“…Similar was observed in Sr 1−x Ca x RuO 3 and Fe doped GeTe thin films [26,27]. It should be noted that this bifuraction is different from spin-glass behavior which usually appears at temper ature far below T C [28,29]. NdNiC 2 exhibits a a spinflop transition from AFM to FM state in magnetic field (figure 1(c)); the crossover field is about 37 kOe at 1.8 K and the easy axis of magnetization direction is along the a-axis [20].…”

Heat-Treatment-Induced Compositional Evolution and Magnetic State Transition in Magnetic Chalcogenide Semiconductor GeFeTe without Structural Phase Change

“…Nevertheless, we cannot exclude the possibility of the formation of atomic-scale Fe clusters. The process of TM aggregation in DMSs, referred to as spinodal decomposition, could provoke the formation of nano or atomic-scale clusters, which are hard to detect by conventional XRD. − As for DMS GeFeTe, Fe clusters are considered to exist in polycrystalline films, while these clusters cannot be detected by XRD or TEM . To further investigate the magnetic behavior of annealed Ge 0.72 Fe 0.28 Te films (S4A), the M vs H curve for sample S4A measured at 300 K is shown in Figure d (inset).…”

“…51−53 As for DMS GeFeTe, Fe clusters are considered to exist in polycrystalline films, while these clusters cannot be detected by XRD or TEM. 53 To further investigate the magnetic behavior of annealed Ge 0.72 Fe 0.28 Te films (S4A), the M vs H curve for sample S4A measured at 300 K is shown in Figure 6d (inset). This curve shows a loop with almost zero coercive field, which is a typical characteristic of ferromagnetic metal clusters formed in a semiconductor matrix.…”

The Aubry–André model as a hobbyhorse for understanding the localization phenomenon

“…Finally, in this paragraph we want to briefly summarize some of the reported predictions of the Aubry-André model. These include spin-orbit coupling effects [41], closed expressions for the energy separating localized and non-localized states [42] and coexistence of localized and extended states in interacting quasiperiodic systems [43] among others. At the many-body level, localization of the ground state is established rigorously in the weakly interacting regime for both repulsive and attractive interactions [44] and many-body localization versus thermalization and onset of equilibrium [45], which can have implications for quantum devices and quantum computation.…”