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Ge 2 Sb 2 Te 5 (GST), a phase change material, generally exhibits two-step crystallization (amorphous → fcc → hcp) to store and process data. The present study reports the crystallization behavior and bonding mechanism of Ga-doped GST thin films with thermal annealing. Ga doping results in the formation of Ga–Te bonds and shows no bonding with other host elements (Ge and Sb), which changes the bonding mechanism and leads to one-step crystallization (amorphous → fcc). The optical transmission contrast confirmed the thermal stabilization of the fcc phase with thermal annealing. These findings suggest that Ga doping into GST thin films has thermally stabilized the metastable fcc phase and suppressed the hcp phase, hence posing it as a potential candidate for phase change memory applications with fast processing speed and low power consumption. [ABSTRACT FROM AUTHOR]

The effects of disorder on the magnetic phases as well as on the conduction process are extensively studied in LaFeO3 nanoparticles in a wide field and temperature ranges. The disorder induced by Na in LaFeO3 alters its robust magnetic phase to the coexistence of distinctly different magnetic orders. The phase purity of the samples, which plays an important role, is detected by synchrotron x-ray diffraction. Detailed magnetic measurements are carried out to investigate the evolution of phases due to substitutions. The samples show the coexistence of a superparamagnetic phase along with a weak ferromagnetic phase, and the ratio of the two distinct phases varies with substitutions. The Mössbauer measurement supported the said magnetic phases in the samples. The X-ray photoelectron spectroscopy analysis clarifies the simultaneous presence of Fe3+ and Fe4+ due to Na+ incorporation. Furthermore, the electrical conduction is found to be greatly influenced by such substitutional disorder. From the dielectric measurement, a p-type polaronic conduction mechanism is found in 25% Na incorporation, which is mainly due to the hole hopping between Fe4+ and Fe3+ states. The semicircles in the whole temperature range in the Cole–Cole plots of impedance and modulus spectra are the co-contribution of the grain and the grain boundary effect in the conduction process. [ABSTRACT FROM AUTHOR]