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In this work, Bi1−x Ca x FeO3 (for x = 0.00–0.30) single-phase thin films were developed on clean glass substrates via simple spray pyrolysis technique. The microscopic crystal structure and magnetic characteristics of the Ca modified thin films were investigated. X-ray diffraction study confirms the hexagonal structure with the space group R3c for all the prepared thin film samples. The crystallite sizes and lattice strains were computed by using the Williamson–Hall plot. The morphology of the samples was viewed by field emission scanning electron microscopy which shows that the average size of grains systematically decreases with the addition of Ca atom at Bi site. The compositions of samples were confirmed by using energy dispersive spectroscopy. The structural phase transition and the position of different Raman modes were observed by using the Raman spectroscopy technique. The elementary compositions, different oxidation states, and the effect of oxygen vacancies of the elements were observed by x-ray photoelectron spectroscopy. The magnetic field (H) dependence of magnetization (M) (i.e. M–H hysteresis loops) of the pure bismuth ferrite (BFO) and Ca doped BFO thin film samples conducted at room temperature using a vibrating sample magnetometer with an applied magnetic field of ±30 kOe and confirmed that the value of magnetization significantly increases with Ca addition at Bi-site in BFO atom. The maximum value saturation magnetization of 3.8176 emu g−1 and remanent magnetization of 0.1408 emu g−1 obtained for the 25% Ca doped BFO thin films.

The FeCoCrNiMnAlx (x = 0.5, 0.75) high-entropy alloy coatings were produced by laser cladding method, and the influence of phase transition was studied. The density and distribution of dislocation, the evolutions of phase and microstructure were investigated by using EBSD, XRD and TEM. Results presented that the higher content of Al element not only refined the grain size of the cladding layer, but also promoted the transition from FCC phase to BCC phase. All the phases in the FeCoCrNiMnAlx (x = 0.5, 0.75) cladding layers developed serious lattice distortions. The anti-plastic deformation ability of the FeCoCrNiMnAl0.75 cladding layer was effectively improved due to the accumulation of a large number of dislocations in the soft FCC phase. The yield strength and tensile strength of the FeCoCrNiMnAl0.75 cladding layers were improved significantly under the joint action of fine-grain strengthening, lattice distortion enhancement, dislocation strengthening and solid-solution strengthening.

Current generations of FinFET devices are incorporating SiGe alloys as stressor material in chan- nel regions in order to enhance hole mobility, drive current and channel conductivity. However, the presence of SiGe gives rise to new issues to be controlled during the device fabrication process, such as the strain retention or defectivity control, since they may seriously impact the quality of the strained SiGe channel and so the final device performance. The present work addresses the study of defect formation during the optimized integration of SiGe FinFETs for 10 nm technology nodes, aimed at determining the Ge threshold content for the nucleation of defects. Due to the relevance of atomistic models in determining the mechanisms and nature of defect formation, Molecular Dynamics (MD) simulations have been performed to emulate the FinFET fabrication process. The channel region is generated by removing a portion of the total volume of the Si substrate, further refilled with Si1-xGex alloy to form the co-integrated FinFETs. After deposition, the presence of Ge induces a lattice distortion which is expected to be relived by defect formation. Samples are annealing varying the Ge fraction, allowing to determine that threshold Ge content for the nucleation of defects is x=0.27. MD provides also the nature of the formed defects, which have been determined to be twinning developed at {111} planes and 60o misfit dislocations. Simulation results have been compared to experimental observations, both in good agreement.

A spintronic theory is developed to study the effect of lattice distortion on the magnetic tunnel junctions (MTJs) consisting of single-crystal barrier and half-metallic electrodes. In the theory, the lattice distortion is described by strain, defect concentration and recovery temperature. All three parameters will modify the periodic scattering potential, and further alter the tunneling magnetoresistance (TMR). The theoretical results show that: (1) the TMR oscillates with all the three parameters; (2) the strain can change the TMR about 30%; (3) the defect concentration will strongly modify the periodic scattering potential, and further change the TMR about 50%; and (4) the recovery temperature has little effect on the periodic scattering potential, and only can change the TMR about 10%. The present work may provide a theoretical foundation to the application of lattice distortion for MTJs consisting of single-crystal barrier and half-metallic electrodes.

The microstructure of NiAl matrix high temperature lubricating composites containing BaO/TiO2 metallic oxides were investigated. The NiAl-BaO/TiO2 composites were fabricated by vacuum hot-pressing sintering. The diffraction peaks of NiAl slightly shifted to the left with the addition of BaO/TiO2 metallic oxide. The crystal plane distance of NiAl phase in the composite was bigger than that in NiAl material according to the Bragg equation. Meanwhile, the lattice distortion and dislocation occurred in the composite structure, which is probably due to the Ti element dissolve in the NiAl matrix during sintering. The cohesive energy and formation enthalpy of NiAl were improved with the incremental of Ti solution contents through density functional theory calculations, which was indicated that the Ti element could dissolve in the NiAl and was in good accordance with the results of XRD and TEM.

In this study we report the deformation microstructures and strength of medium entropy alloys (MEAs) and high entropy alloys (HEAs), which are defined as alloys composed of four or less, and five or more principal elements, respectively, with (near-) equi-atomic concentrations. The friction stress (fundamental resistance to dislocation motion in the crystal lattice) and Hall-Petch relationship of various MEAs (CoCrFeNi, CoCrNi, etc.), taken as subsystems of the equi-atomic CoCrFeMnNi HEA, were precisely measured at room temperature. Experimental values of the friction stresses were found to fit with a theoretical model proposed by Toda-Caraballo et al. very well, which indicates that the strength of the alloys is closely related to a heterogeneously distorted crystal lattice. At the same time, values of the average lattice distortion in the alloys were found to be comparable to those in some dilute alloys, contradicting the belief that “severe” lattice distortion is a reason for the higher strength than in dilute systems. Finally, a strengthening mechanism due to element-element interactions was proposed as an additional mechanism in FCC HEAs and MEAs.

The kinetics of lattice distortion introduction and lattice relaxation at the surface of thermally-oxidized 4H-SiC (0001) were investigated. Our results suggested that lattice distortion introduction and lattice relaxation seem to follow zeroth and second order rate laws, respectively. The obtained activation energy of ~3.9 eV for lattice distortion introduction and ~1 eV for its relaxation indicate that the lattice distortion is determined by a bond rearrangement or movement process with a relatively low activation energy. Furthermore, the formation of byproducts which remain at the surface region of 4H-SiC was predicted to be a possible origin of the significant lattice distortion.

In this study, the effects of the addition of Zn on the microstructures, thermal and electrical conductivity of as–cast Mg–4Y–xZn (x = 1, 2, 3, and 4 wt%) alloys were investigated. Results reveal that with the increase of Zn content, the second–phase transformation from the X phase to the W phase occurs. Except for the WZ43 alloy, the amount of solute atoms in the α–Mg matrix decreases with the increase of Zn, leading to the decreased lattice distortion and increased thermal conductivity. Therefore, the obtained highest electrical and thermal conductivity of the WZ44 alloy are 13.73 S m−1 and 95.61 W m−1 K−1, respectively. The correlation between the electrical conductivity and the thermal conductivity was characterized by the equation λ = 0.890L 0 Tσ + 6.96 on the basis of the Smith–Palmer equation.

Local lattice distortions at the surface of 4H-SiC(0001) after various thermal oxidation processes were investigated by in-plane X-ray diffractometry. Our results showed that dry oxidation induced lattice distortion, observed as the increase of interplanar spacing, became higher with increasing oxidation time. Lattice constant changes of up to ~0.4% were observed by increasing the oxide thickness to 44 nm. This lattice distortion was not recovered after removal of the SiO2 layer by chemical etching, although it was partially reduced by Ar gas annealing, suggesting that strain relaxation requires removal of oxidation-induced defects in the 4H-SiC surface region.

We present different relaxation mechanisms of Ge and SiGe quantum dots under excimer laser annealing. Investigation of the coarsening and relaxation of the dots shows that the strain in Ge dots on Ge films is relaxed by dislocation since there is no interface between the Ge dots and the Ge layer, while the SiGe dots on Si0.77Ge0.23 film relax by lattice distortion to coherent dots, which results from the obvious interface between the SiGe dots and the Si0.77Ge0.23 film. The results are suggested and sustained by Vanderbilt and Wickham's theory, and also demonstrate that no bulk diffusion occurs during the excimer laser annealing.

A series of Fe2YSi (Y = Cr, Mn, Fe, Co, Ni) alloys were synthesized and their electronic and magnetic properties were studied both theoretically and experimentally. In particular, a novel Heusler alloy Fe2CrSi single phase was synthesized by means of the melt-spinning method. First principles FLAPW calculations were performed on Fe2YSi alloys. Based on the results, Fe2CrSi is predicted to be a half-metallic ferromagnet with a spin moment of 2?B/f.u. and a gap of 0.42?eV. Fe2MnSi is also half-metallic in the ferromagnetic state. The saturation magnetic moments at 5?K for this series of alloys fit the theoretical calculations well. Specifically, the saturation magnetic moment of Fe2CrSi is 2.05?B/cell, which agrees with the ideal value of 2?B derived from the Slater?Pauling rule. The Curie temperatures of Fe2YSi alloys are all higher than 500?K except for Fe2MnSi, which has a TC below room temperature. Finally, the effect of lattice distortion on the electronic and magnetic properties of Fe2CrSi and Fe2CoSi was studied. It is found that Fe2CrSi is half-metallic from ?3% to +1% uniform lattice distortion, and this character is preferred in systems containing large strain, such as melt-spun ribbons or thin films.

The thermoelectric power (TEP) measurements have been carried out to investigate the changes in the electronic structure associated with the intermartensitic and martensitic transitions in Ni$_{2+x}$Mn$_{1-x}$Ga (0 $\le$ x $\le$ 0.19). The samples have been characterized by a.c. magnetic susceptibility measurements. The correlation between the TEP and the microstructural changes sensitive to the increasing Ni content in Ni$_{2+x}$Mn$_{1-x}$Ga has been investigated. The changes in the density of states as reflected in the temperature variation of the TEP are consistent with the conclusions drawn from the Jahn-Teller mechanism of lattice distortion., 11 pages, 5 figures; Accepted for publication in J. Phys. Condens. Matter (2006)

We have investigated Sr1−xLax/2Kx/2RuO3 and Sr1−xPbxRuO3, which have a larger average size of the A-site cations. They manifest a gradual loss of ferromagnetism in a similar way as their counterparts with smaller A-site cations. There is also evidence for a magnetism-suppressing disorder effect similar to that observed in Sr1−xLax/2Nax/2RuO3. Therefore, the Stoner ferromagnetism in SrRuO3 is rather unique and cannot be easily tuned by lattice distortion to yield a higher Curie temperature.

Colloidal CdSe/ZnSe core/shell nanocrystals were prepared via the conventional TOP/TOPO process and their shell thickness was controlled varying the ZnSe precursor concentration. X-ray diffraction (XRD) on the nanocrystals showed gradual peak shifts to high two-theta angles due to a decrease in the lattice parameter of CdSe cores with an increase in the ZnSe shell thickness. High-resolution transmission electron microscopy (HRTEM) images of the CdSe/ZnSe nanocrystals show a c-axis elongation with an increase in ZnSe precursor concentration and crystalline defect formation in some of the nanocrystals with 2.0 mM ZnSe precursor concentration, possibly due to high compressive strain. Photoluminescence (PL) spectra of the CdSe/ZnSe nanocrystals showed an increase in the peak intensity up to 1.0 mM ZnSe precursor concentration due to the surface passivation effect, and a decrease beyond this value, possibly due to the formation of crystalline defects such as stacking faults. The PL wavelength showed red-shifts up to 1.0 mM ZnSe precursor concentration due to the partial leakage of an electron wavefunction of CdSe cores into the ZnSe shells and blue-shifts beyond this value due to the high compressive strain from the ZnSe shells.

In this paper, the relation between the dielectric properties and the lattice distortion in the phase coexistence region is discussed using a phase statistical distribution model, and in the rhombohedral phase region the two connection equations on the dielectric properties and the lattice distortion are established. Particularly, the relation between the dielectric properties and the lattice distortion is investigated in the phase coexistence region of PZT ceramics, and the fitting value of the volume fraction of the tetragonal phase VT to composition x in the equation is determined. Further, the fitting results are well consistent with the related experimental data. It involves more profound physical process than relation between the dielectric properties and composition x.

In the present paper, we continue our investigation on the antiferromagnetic origin of the charge order observed in the half-doped manganese. By introducing a Su–Schrieffer–Heeger (SSH) type of perturbation interaction to the double-exchange Hamiltonian, we calculate again its ground-state phase diagram at filling x = 0.5 by the unrestricted real-space Hartree–Fock approximation method. We find that, as the SSH electron-phonon interaction increases, the charge order parameter decreases to zero rapidly but the CE-type antiferromagnetic order becomes more stable. In other words, the charge order is much more fragile than the CE-type or the Neel-type antiferromagnetic orders under the electron-phonon perturbation. These results support the proposed theory in the recent publications that the charge order in these systems is induced by the antiferromagnetic correlations.

The low-and high-temperature structures of La2CoMnO6 and La2NiMnO6 have been refined using powder neutron diffraction. At low temperatures the materials adopt a charge-ordered monoclinic structure which transforms to a rhombohedral structure at elevated temperature without loss of charge ordering. This charge ordering scheme allows us for the first time to rationalize the relationships between the physical and structural properties of these materials.

The lattice parameters of tetragonal strontium titanate are determined to about 1 part in 106 with penetrating X-rays. While no peculiarity is detected in a bulk sample, a distinct anomaly at 37 K is observed in an optically polished thin platelet derived from the same single crystal. This suggests that the anomaly is related to a high density of dislocations. A possible mechanism is that dislocations stabilize transverse antiphase boundaries which undergo a ferroelectric transition near 37 K. If so, this transition stresses the boundaries which then strain the bulk leading to the observed anomaly.

Energy-dispersive x-ray diffraction measurements have been carried out in the perovskite La0.5Ca0.5MnO3 and bismuth-doped La0.25Bi0.25Ca0.5MnO3 under hydrostatic pressure in a diamond cell. On the substitution of La3+ ion with Bi3+ ion, a shoulder peak appears in the observed main peak of La0.25Bi0.25Ca0.5MnO3 at 43.9 GPa, but not in that of La0.5Ca0.5MnO3 with the pressure up to 45.9 GPa. This phenomenon can be explained by a number of discrete clusters that are simultaneously present in the sample, due to the pressure enhanced interactions between charge, orbital and coupling with the lattice distortion coming from the unique 6s2 lone-pair characteristics of Bi3+.

We report results of nuclear quadrupole resonance (NQR) experiments on the Re sites in the pyrochlore superconductor Cd2Re2O7. A discontinuous change of the NQR spectrum was observed near T s2 = 120 K, confirming the first-order structural transition in addition to the already known second-order transition at T s1 = 200 K. The spin?lattice relaxation rate at the Re sites shows a steep increase above T s2, in contrast to the reported results for the Cd sites, suggesting changes of orbital fluctuations.

The Mg diffusion method with the MgB4 addition is carried out to improve the MgB2 application performance. The precursor B powders and MgB4 powders are uniformly mixed as the ratio of (1- 4x) : x mol %, (x = 0, 1, 2, 5, 10 and 20). The mixed powders are pressed into bulks and the excess of Mg powders are added into the iron pipe. Then the heat treatment is carried out under the pure argon atmosphere. Finally, the high-quality MgB2 bulks are achieved with high density. The superconducting critical temperature of the MgB2 bulks decreases slightly with the increase of MgB4 addition content. However, the critical current density increases significantly at the high-fields. It is perhaps due to the small-sized MgB4 impurities in MgB2 bulk function as effective pinning centers and generates significant lattice distortion in the MgB2 lattice to yield improved J c performance in the applied field. It suggests that further improvement in the superconducting properties of the MgB2 added with the MgB4 will be possible via a better control of the composition and processing parameters. This also provides a reference for improving the preparation of MgB2 wire.

Ultraviolet–ozone (UVO) and oxygen plasma are widely used to modify the surface of materials because these processes are facile and accessible. These dry oxidation treatments are also commonly applied to 2D graphene and are presumed to induce similar oxidation effects on the graphene surface. However, in this work, these treatments are revealed to induce the formation of different types of defects on the surface of graphene because the UVO treatment causes a chemical reaction, whereas the oxygen plasma treatment causes both physical and chemical reactions. The oxygen plasma treatment results mainly in topological defects, which effectively induce the attachment of oxygen atoms onto the treated surface; by contrast, the UVO treatment induces only the attachment of oxygen atoms onto the treated surface, without inducing lattice distortion. These results are confirmed mainly by atomic-resolution transmission electron microscopy imaging and electron energy loss spectroscopy. Using such facile dry oxidation treatments, we experimentally modified the surface states of graphene at the atomic scale.

Properties of deep-level defects in CuGaSe2 thin-film solar cells were investigated using transient photo-capacitance (TPC) spectroscopy. Two Gaussian-shaped deep-level defects centered at around 0.8 eV and 1.54 eV above the valence band were identified. The electronic structure of the two defects was illustrated by a configuration coordinate model to explain the thermal quenching effect in the two defects, which considered a large lattice distortion for the 0.8 eV defect while no distortion for the 1.54 eV defect.

The N and C doping effects on the crystal structures, electronic and optical properties of fluorite structure CeO2 have been investigated using the first-principles calculation. Co-doping these two elements results in the local lattice distortion and volume expansion of CeO2. Compared with the energy band structure of pure CeO2, some local energy levels appear in the forbidden band, which may facilitate the light absorption. Moreover, the enhanced photo-catalytic properties of CeO2 were explained through the absorption spectra and the selection rule of the band-to-band transitions.

Recent reports, that the samples of nominal compositions, La1-xCexMnO3, form single-phase compounds with orthorhombically distorted perovskite structure, are questionable. Our studies on the sample of nominal composition, La0.7Ce0.3MnO3, and careful analysis of the structural data available in the literature, suggest that the above mentioned samples actually form multi-phase mixtures comprising hole doped lanthanum deficient lanthanum manganate phases and cerium oxide (CeO2).

Novel dimerized antiferromagnetic (homogeneous spin-Peierls) and inhomogeneous-lattice antiferromagnetic (inhomogeneous spin-Peierls) ground states are found in a one-dimensional (1-D) and a two-dimensional (2-D) electron-lattice periodic Anderson model, respectively. Coexistence and mutual enhancement of the Peierls lattice distortion and the antiferromagnetic long-range-order are emphasized. The stoichiometric (half-filling) phase diagrams for the 1-D and 2-D cases are strongly dependent on the hybridization and electron-lattice coupling. For non-stoichiometric fillings, local lattice distortion (coupled spin-charge-lattice small-polaron) states are found: these are discussed in the context of, for example, Ce-based, heavy-fermion systems. Relations to volume collapse phenomena and inorganic spin-Peierls systems, and the similarity of the phase diagrams to those of organic superconductors are also described.

The growth-temperature dependence of the transition structure at the SiO2/Si interface is studied by high-resolution Rutherford backscattering spectroscopy/channeling. A Si lattice distortion is found at the interface. Such distortion propagates more than 2 nm from the interface. It is shown that the SiO2/Si grown by wet oxidation at 1100 °C has a smaller lattice distortion than that grown at 900 °C. This can be explained in terms of the relaxation of the strained SiO2 network caused by the viscous flow of SiO2 at high temperatures.

We report the first direct observation of an incommensurate lattice distortion in dielectric crystals by an atomic-force microscope. The layered crystal (NH3C3H7)2MnCl4 has been imaged in the normal and incommensurate phases. In the normal phase, we observe well-ordered atomic corrugations on a cleavage surface of a crystal. In the incommensurate phase, these atomic corrugations are modulated by a long periodic plane-wave distortion.

We applied atomic force microscopy (AFM) to study the surface morphology of ferroelectric BaTiO3 (barium titanate, BT) and NaKC4H4O64H2O (Rochelle salt, RS). At room temperature, an undulation of the crystal surface was observed around the 90° domain boundary in BT and around the monoclinic domain boundary in RS.

The effect of minor changes in lattice parameters and ratios on the magnetoresistive and related properties of the La - Er - Ca - Mn - O perovskite system have been investigated. The latter is found to be the more important factor in determining the magnetotransport properties of these materials. One composition has been prepared by both the standard ceramic method as well as a sol - gel technique. Although the general features of the magnetotransport properties of these two samples were very similar, the magnetic properties showed significant differences. Experimental results are explained on the basis of a spin-dependent mechanism which is related to lattice distortion.

We study here the effect of local lattice distortion on the electronic structure of non-isochoric alloys with large size difference between the constituents using the augmented space recursion. In particular we study such effects in CuPd and CuBe alloys.

Bulk nanocrystalline selenium (nc-Se) samples were prepared by crystallizing as-quenched amorphous selenium (a-Se). The structure of nc-Se was investigated by x-ray diffraction (XRD) and transmission electron microscopy (TEM). nc-Se samples are of trigonal structure with grain sizes ranging from 8.4 to 27.8 nm. Direct TEM observations showed that nc-Se consists of lamellae which are made up of fibres with a nanometre-sized thickness. A lattice distortion was revealed in nc-Se from quantitative XRD measurements, i.e., the lattice parameter a increases and c decreases simultaneously with a reduction in grain size. For the samples with grain sizes smaller than 12 nm, the unit cell volume is expanded; but it is contracted for those with grain sizes larger than 12 nm. A change of elastic modulus with grain size is inferred from the change of unit cell volume.

We have investigated the stability of the antiferromagnetic order in the ground state of the two-dimensional Heisenberg model against a lattice dimerization produced by the electron-lattice interaction. Unlike the one-dimensional case, we found that a critical coupling is required to form a dimerized state via a first-order phase transition. We have also considered the combined effects of frustrating second-neighbour interactions and lattice dimerization in destroying the Neel order. Our approach is based on the Schwinger representation of spin operators, and is in excellent quantitative agreement with exact numerical results on finite lattices.

We have studied the room temperature and low-temperature electrical resistivities of nanocrystalline Fe-Cu-Si-B alloys with various grain sizes prepared by crystallization of amorphous material. Experimental results showed that with the reduction of grain size both room temperature resistivity rho(RT) and residual resistivity rho0 of the nanostructured alloys studied increased significantly. Based on the scattering effects from interfaces and lattice distortion, the above results were qualitatively discussed.

We have combined extended X-ray absorption fine structure (EXAFS) and electron diffraction to study both ordered and disordered Cu3Pd, and have established that in the first shell of neighbours the Cu-Pd distance is ~ 0.03 A greater than that for Cu-Cu. This result lends support to recent theoretical treatments which assume a distribution of bondlengths in disordered alloys, and draws attention to the fact that Vegard's law does not require a single, mean bondlength, as assumed in the application of mean-field theories.

On the basis of recently published data for the martensitic transformations in Cu-Zn-Al alloys, an evaluation of the phase stabilities of martensitic and equilibrium phases in other noble-metal alloys has been made. The contributions which control the Gibbs energy of the different phases are discussed quantitatively. The most important of these are the stability of the disordered phases, the vibrational entropy, the influence of the long-range order characterized by pair interchange energies, the structure-dependent lattice distortions and the energies associated with the stacking sequences in the different close-packed phases.

Ferroelectric crystals possess memory functions in their thermal, mechanical, electric and optic properties due to the ferroelectric-paraelectric phase transformation. The dependence of the transformation temperature upon the applied electric fields and mechanical loads renders these crystals desirable materials for the design of smart sensors and actuators. A continuum model for predicting this behavior is proposed. The analysis indicates that the stress dependence of the transformation is determined by the lattice distortion of the crystal associated with the corresponding structural transformation. Some of the predictions are in qualitative agreement with experimental observation.

We derive a semi-microscopic model for a mixed crystal with orientable molecules in the presence of lattice anisotropy. Fluctuations in the orientational degrees of freedom can be related exactly to fluctuations in the strain field. The phase diagram is calculated approximately: depending on the degree of disorder, we find either a state with long-range orientational order and a uniform lattice distortion or a glassy state. Enhanced orientational fluctuations near the transition give rise to a pronounced softening of the lattice in symmetry directions, which are determined by the anisotropy fields.

Self-consistent tight-binding supercell calculations of localised defect levels and nearest-neighbour relaxations are presented for Cd, Hg and In interstitials at tetrahedral and hexagonal sites in CdTe and HgTe. The mechanisms driving the relaxation and the resulting character of the lattice distortion about various interstitials are insensitive to the alloy composition and should remain valid for interstitials in Hg-rich HgCdTe.

Holes introduced into high gap materials by acceptor doping are often self-localized at anion sites as small polarons bound to the doping elements. The related lattice distortion lowers the hole energy; the hole levels thus tend to be deep. Electronic structure calculations of small polarons have identified, for some dopings, that such localized states can coexist with extended ones that result from the same doping. Using a scaling formalism, proposed by Emin and Holstein, it is shown that this appears to be a general phenomenon if the polaron-forming short-range hole–lattice coupling is taken into account.

A kind of extended line defect is currently an experimentally available one-dimensional topological structure in graphene lattice. It modifies the electronic properties of graphene in many aspects. For example, it induces an even-parity boundary state which has linear dispersion and breaks the electron-hole symmetry of the graphene electronic structure. In addition, the line defect possesses much stronger adsorption ability to the metal adatoms than the ordinary graphene lattice point. In the present work, by developing an analytical lattice Green's function technique, we theoretically study the RKKY interaction in graphene when two magnetic impurities are adsorbed near the line defect. We find that R(-3) decay rate of the RKKY interaction unique to graphene still holds true in the presence of the line defect. But another feature of the RKKY interaction in graphene, referred to as the Saremi's rule, which claims the RKKY interactions between the same or opposite sublattice points are ferro- or antiferromagnetic respectively, is no longer preserved due to the influence of the boundary state around the line defect. More importantly, the RKKY interaction on the line defect is greater than its counterpart in the pristine graphene by about one or two orders of magnitude. The local lattice distortion around the line defect can bring about the transition of the RKKY interaction between ferro- and antiferromagnetic orders. Such a result implies that the presence of the extended line defect provides a feasible platform in graphene to realize the long-range magnetic order even at a high temperature.

The lattice parameter changes in three types of Nb3Sn superconducting wires during uniaxial stress–strain measurements at 4.2 K have been measured by high-energy synchrotron x-ray diffraction. The nearly-stress-free Nb3Sn lattice parameter has been determined using extracted filaments, and the elastic strain in the axial and transverse wire directions in the different wire phases has been calculated. The mechanical properties of the PIT and RRP wire are mainly determined by the properties of Nb3Sn and unreacted Nb. This is in contrast to the bronze route wire, where the matrix can carry substantial loads. In straight wires the axial Nb3Sn pre-strain is strongest in the bronze route wire, its value being smaller in the PIT and RRP wires. A strong reduction of the non-Cu elastic modulus of about 30% is observed during cool-down from ambient temperature to 4.2 K. The Nb3Sn Poisson ratio at 4.2 K measured in the untwisted bronze route wire is 0.35. The present study also shows that the process route has a strong influence on the Nb3Sn texture.

During the sputtering process, the bombardment effect of negative oxygen ions (NOIs) on the thin-film properties of amorphous indium gallium zinc oxide (a-IGZO) was investigated. The energies of NOIs determined by in situ ion energy analyses are in good agreement with the values obtained using the Meyer equation. Furthermore, we find that the energies of NOIs are sufficiently high to affect the lattice distortion and/or displacement in a-IGZO films. The overall analysis revealed that the bombardment of NOIs has a considerable effect on a-IGZO film properties. Our work demonstrates that the bombardment of NOIs is a crucial issue for achieving high-quality a-IGZO films.

The interlayer transport of an electron in bilayer graphene influenced by a phonon in the presence of a biased potential is investigated using the tight-binding approach. The in-plane optical mode E2g and out-of-plane optical mode B1g associated with the applied biased potential are considered to compute and discuss the interlayer transport probability of an electron initially localized on the bottom layer at the Dirac point in the Brillouin zone. Without the biased potential, the interlayer transport probability is equal to 0.5 regardless of the phonon displacement except for a few special cases. Applying a biased potential to the layers, we find that in different phonon modes the function of the transport probability with respect to the applied biased potential and phonon displacement is complex and various, but on the whole the transport probability decreases with the increase in the absolute value of the applied biased potential. These phenomena are discussed in detail in this paper.

We report on the structural transformation and unique magnetic properties of manganese nitrides prepared by nitriding Mn under N2 pressures of up to 25 MPa with varying temperatures. High N2 pressure not only makes nitridation more efficient at lower temperatures, but also enhances the N-content in the nitride lattices, which were expanded with increasing N-content. The N-rich nitrides, including e-Mn4N, ζ-Mn6N2.58 and η-Mn3N2, exhibit unique thermal behaviors. The N-rich e-phase exhibits much larger coercivity and lower saturation magnetization in comparison with the e-phase prepared under ambient N2 pressures. The coercivity of the N-rich ζ-phase reaches up to 45054 A/m. A saturation magnetization as large as 31 Am2/kg is observed in the N-rich η-phase. Both are quite different from the conventional antiferromagnetic ζ- and η-phase obtained under ambient N2 pressures. We ascribe the unconventional magnetic properties of the nitrides to the lattice distortion originating from the N-enrichment.

The behavior of lattice distortion in spin 1/2 antiferromagnetic XY models with random magnetic modulation is investigated with the consideration of spin—phonon coupling in the adiabatic limit. It is found that lattice distortion relies on the strength of the random modulation. For strong or weak enough spin—phonon couplings, the average lattice distortion may decrease or increase as the random modulation is strengthened. This may be the result of competition between the random magnetic modulation and the spin—phonon coupling.