Synthesis and Characterization of Functional Magnetic Nanomaterials

Nanoscale materials have grabbed the attention of researchers from a fundamental and application point of view for over a century [...

Strong Deep-Level-Emission Photoluminescence in NiO Nanoparticles

Nickel oxide is one of the highly promising semiconducting materials, but its large band gap (3.7 to 4 eV) limits its use in practical applications. Here we report the effect of nickel/oxygen vacancies and interstitial defects on the near-band-edge (NBE) and deep-level-emission (DLE) in various sizes of nickel oxide (NiO) nanoparticles. The ultraviolet (UV) emission originated from excitonic recombination corresponding near-band-edge (NBE) transition of NiO, while deep-level-emission (DLE) in the visible region due to various structural defects such as oxygen vacancies and interstitial defects. We found that the NiO nanoparticles exhibit a strong green band emission around ~2.37 eV in all samples, covering 80% integrated intensity of PL spectra. This apparently anomalous phenomenon is attributed to photogenerated holes trapped in the deep level oxygen vacancy recombining with the electrons trapped in a shallow level located just below the conducting band

Structural and Superconducting Proximity Effect of SnPb Bimetallic Nanoalloys

We report the superconducting properties between a conventional strong-coupled Pb and weak-coupled Sn superconductor. A series of SnrPb1-r nanoalloys with various compositions r were synthesized, and their superconducting properties were measured using superconducting quantum interference devices (SQUIDs) magnetometer. Our results reveal a superconducting proximity effect (SPE) between immiscible Sn and Pb granules in the range of r = 0.2~0.9, as a weak superconducting coupling can be established with the coexistence of phonon hardening and increased Ginzburg–Landau coherence length. Furthermore, our results provide new insights into improving the study of the superconducting proximity effect introduced by Sn doping

Room Temperature Magnetic Memory Effect in Nanodiamond/γ-Fe2O3 Composites

We report a room temperature magnetic memory effect (RT-MME) from magnetic nanodiamond (MND) (ND)/γ-Fe2O3 nanocomposites. The detailed crystal structural analysis of the diluted MND was performed by synchrotron radiation X-ray diffraction, revealing the composite nature of MND having 99 and 1% weight fraction ND and γ-Fe2O3 phases, respectively. The magnetic measurements carried out using a DC SQUID magnetometer show the non-interacting superparamagnetic nature of γ-Fe2O3 nanoparticles in MND have a wide distribution in the blocking temperature. Using different temperature, field, and time relaxation protocols, the memory phenomenon in the DC magnetization has been observed at room temperature (RT). These findings suggest that the dynamics of MND are governed by a wide distribution of particle relaxation times, which arise from the distribution of γ-Fe2O3 nanoparticle size. The observed RT ferromagnetism coupled with MME in MND will find potential applications in ND-based spintronics

Strong electron-phonon coupling in superconducting bismuth nanoparticles

We report on the nanosized effect on superconducting properties of Bi nanoparticles (NPs) that extracted from the temperature and applied magnetic field dependent magnetization measurements of bismuth NPs, and revealed an enhanced TC and stronger coupling strength because of increased density of state and softened phonons ωln. A strong electron-phonon coupling (λep = 1.639) to low-lying phonons (ωln = 58 K) is found to be the leading mechanism behind the observed superconductivity with an enhanced TC ∼ 8.22 K and a strong superconducting coupling strength of α = 2.32(1) of 15 nm Bi NPs. Our results are well described by the Allen and Dynes formula within the framework of the McMillan formalism and are in agreement with the Ginzburg-Landau theory calculations

Room Temperature Magnetic Memory Effect in Cluster-Glassy Fe-Doped NiO Nanoparticles

The Fe-doped NiO nanoparticles that were synthesized using a co-precipitation method are characterized by enhanced room-temperature ferromagnetic property evident from magnetic measurements. Neutron powder diffraction experiments suggested an increment of the magnetic moment of 3d ions in the nanoparticles as a function of Fe-concentration. The temperature, time, and field-dependent magnetization measurements show that the effect of Fe-doping in NiO has enhanced the intraparticle interactions due to formed defect clusters. The intraparticle interactions are proposed to bring additional magnetic anisotropy energy barriers that affect the overall magnetic moment relaxation process and emerging as room temperature magnetic memory. The outcome of this study is attractive for the future development of the room temperature ferromagnetic oxide system to facilitate the integration of spintronic devices and understanding of their fundamental physics