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α-SiAlON ceramics have been in use as engineering ceramics in the most arduous industrial environments such as molten metal handling, cutting tools, gas turbine engines, extrusion molds, thermocouple sheaths, protective cover for high-temperature sensors, etc., owing to their outstanding mechanical, thermal and chemical stability. Taking advantage of the intrinsic properties of α-SiAlONs, we investigate, in this paper, the possibility of using the Er-doped α-SiAlON (Er-α-SiAlON) ceramic as a high-temperature sensing material via its unique near-infrared to visible upconversion property. We first use neutron diffraction and density functional theory calculations to study the electronic structure and thermodynamic stability of Er-α-SiAlON. It is found that the interstitial doping of Er stabilizes the α-SiAlON structure via chemical bonds with O-atoms with N:O ratio of 5:2 in the seven-fold coordination sites of the Er3+ ion. Temperature-dependent upconversion emissions are then studied under 980 and 793 nm excitations over a temperature range of 298–1373 K and the fluorescence intensity ratio (FIR) technique has been employed to investigate the temperature sensing behavior. Temperature-dependent Raman behavior is also investigated. We demonstrate that using Er-α-SiAlON as a sensing material, the limit of temperature measurement via the FIR technique can be pushed well beyond 1200 K. [ABSTRACT FROM AUTHOR]

Using ab-initio simulations, we investigated the effects of ferroelectric polarization on the magnetic anisotropy of FePt/BaTiO3 heterojunctions. The changed electronic structure at the interface of FePt and BaTiO3 reduced the magnetic anisotropy energy (MAE) under ferroelectric polarization. Through the electronic density of states analysis, it was found that the MAE change is mainly due to the changed hybridization state between d-orbitals of interface Ti and Fe atoms. [ABSTRACT FROM AUTHOR]

Using ab initio calculations, we investigated the changes of the magnetic moment and electronic structures of Fe adatoms on strained graphene sheets. By the uniaxial tensile strains in armchair and zig-zag directions on graphene sheets, the amounts of charge transfers from graphene 2pz orbital to Fe adatom 3d orbitals were linearly increased. The magnetic moments of Fe, however, show the tendency of linear decrements with the uniaxial tensile strains. The increased Fe magnetic moments by uniaxialy graphene compressions resulted from the shifting of spin-minority states of electrons while the decreased Fe magnetic moments were due to the reduction in the spin-majority states of 3dxy-orbitals of the Fe adatom. [ABSTRACT FROM AUTHOR]

Abstract: Using the first-principles calculations, we investigated the structure dependent magnetic properties of graphene-adsorbed magnetic fcc Fe/Ni(111) thin film. The adsorption sites of the graphene carbon atoms were switched from the fcc hollow sites to the on top sites of the Fe surface atoms due to the fcc Ni(111) substrate effect. From the calculated perpendicular magnetic anisotropy energies, the 1ML-Fe was found to have stable surface-normal magnetization while 2 and 3 monolayer Fe between graphene and Ni(111) had in-plane magnetization. From the electron density of state analyses, the thickness-dependent magnetic anisotropy energy and magnetization direction were found to originate from the shifting of up-spin and down-spin electrons in 3dyz and 3dzx toward higher and lower levels, respectively. [Copyright &y& Elsevier]

Abstract: The effects of three crucial structural variations, i.e., sub-monolayer coverage, intermixing, and stacking fault, on the magnetism of Fe/Cu(111) were quantitatively investigated using density functional theory calculations. A single Fe atom (0.25ML) on the fcc (2×2) Cu(111) surface has a higher magnetic moment (3.18μB) than bulk Fe (2.15μB). The calculated magnetic moments of 0.5, 0.75 and 1ML coverage Fe on the Cu(111) surface, were 3.01μB, 2.87μB and 2.72μB, respectively. For intermixing between 1ML of Fe and Cu(111), the magnetic moment of the Fe adatoms monotonically decreased with the intermixing amount. The electron density of states showed that the decreasing magnetic moment of Fe adatoms resulted from the filling of down-spin 3d-electrons below Fermi level by the hybridization of 3d-electron among Fe atoms. The influence of Cu(111) atoms on the electronic structure and magnetic moment was observed to be negligible. In the artificially prepared 2 and 3ML thick Fe films on Cu(111), the magnetic moments of Fe atoms were not dependent on the stacking sequences of Fe layers. However, the demagnetization energy calculation revealed a more stable perpendicular magnetization for fcc Fe films compared to hcp Fe films on Cu(111). In brief, the structure dependence of magnetism of Fe films on Cu(111) mainly originates from the bonding among Fe atoms, while the effect of bonding with Cu atoms was negligible. [ABSTRACT FROM AUTHOR]