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The Li–Mg–N–H system has been identified as a promising hydrogen storage material due to its moderate operation conditions as well as the high capacity and reversibility. Recently Rijssenbeek et al. [J. Alloys Compd. 454, 233 (2008)] reported that Li2Mg(NH)2 has disordered cation and vacancy arrangements at room temperature and above. We present our first-principles calculations to investigate a series of ordered low-energy configurations for this compound. Specific local orderings are found in the cation-vacancy arrangement, shedding light on the experimental disordered structure models. A possible ordered phase at low temperature is proposed based on these local orderings. Reaction energetics and phase stability are further discussed. [ABSTRACT FROM AUTHOR]

The Li–Mg–N–H system has been identified as a promising hydrogen storage material due to its moderate operation conditions as well as the high capacity and reversibility. Recently Rijssenbeek et al. [J. Alloys Compd. 454, 233 (2008)] reported that Li2Mg(NH)2 has disordered cation and vacancy arrangements at room temperature and above. We present our first-principles calculations to investigate a series of ordered low-energy configurations for this compound. Specific local orderings are found in the cation-vacancy arrangement, shedding light on the experimental disordered structure models. A possible ordered phase at low temperature is proposed based on these local orderings. Reaction energetics and phase stability are further discussed. [ABSTRACT FROM AUTHOR]

The electronic and magnetic properties of Co-doped ZnO are investigated based on the B3LYP hybrid spin-density functional method. The calculated electronic structures obtained from B3LYP agree well with the experimental results. B3LYP predicts that antiferromagnetic (AFM) ordering between the Co ions is favored over ferromagnetic (FM) ordering in intrinsic Co-doped ZnO, and reveals that the FM ordering can be induced by electron doping when the doping level reaches 1 electron per Co ion. These results agree well with the FM ordering observed in highly conductive n-type Zn1-xCoxO films. Charge transfer to the minority-spin d states of Co atoms and the consequent double-exchange interaction are the primary origins of FM ordering. Since Ni has one more electron than Co, we also investigate the electronic and magnetic properties of intrinsic Ni-doped ZnO. Qualitatively different from the local-density-approximation results, B3LYP predicts that Ni-doped ZnO is an insulator and favors AFM ordering. [ABSTRACT FROM AUTHOR]

We investigate the formation of compositional modulation and atomic ordering in InGaP films. Such bulk properties—as well as surface morphologies—present a strong dependence on growth parameters, mainly the V/III ratio. Our results indicate the importance of surface diffusion and, particularly, surface reconstruction for these processes. Most importantly from the application point of view, we show that the compositional modulation is not necessarily coupled to the surface instabilities, so that smooth InGaP films with periodic compositional variation could be obtained. This opens a new route for the generation of templates for quantum dot positioning and three-dimensional arrays of nanostructures. [ABSTRACT FROM AUTHOR]

We report the microstructural evolution during irradiation of FePt and FePt 25 at. % thin films sputter deposited onto electron transparent silicon monoxide substrates. The films were studied in situ for 500 keV Kr+ irradiation up to a fluence of 1015 ions/cm2 or 4 displacements/atom (dpa). Upon irradiation to approximately 1 dpa, the initial disconnected granular morphology became continuous. In particular, for FePt, accelerated grain growth was observed once the continuous morphology was achieved during ambient temperature irradiation. No atomistic (chemical) ordering from the as-deposited A1 phase into either the L10 FePt or L12 Fe3Pt phases was observed during ambient temperature irradiation. After irradiation, the specimens were then in situ annealed. The intermetallic ordering temperature, compared to that of an unirradiated film, was lowered by ≈200 °C for FePt 25 at. %. No decrease in the ordering temperature was observed for irradiated FePt. The rate of FePt grain growth during annealing was very similar for both irradiated and unirradiated films over the 25–650 °C temperature range investigated. [ABSTRACT FROM AUTHOR]

Fe-Ga alloys with compositions near 27.5 at. % Ga (26-29 at. %) can be heat treated to obtain ordered phases based on &alpah;″ (ordered bcc), D0[SUB19] (ordered hexagonal), and L1[SUB2] (ordered fcc) structures. This work presents an evaluation of how the different ordering treatments influence the magnetostriction in cast polycrystalline Fe-27.5 at. % Ga alloy. Alloy samples were annealed first in the disordered bcc (A2) phase region to obtain a disordered bcc solid solution, followed by ordering-heat treatment in the appropriate temperature region of stability of each of the ordered phases. X-ray diffraction was used to characterize the phases present prior to and after heat treatments. Magnetostriction measurements were carried out at different prestress levels in the range of 0-50 MPa. Magnetic properties were measured using a vibrating sample magnetometer. Annealed Fe-27.5 at. % Ga sample with a disordered bcc (A2) structure and a weak [110] texture showed a magnetostriction value of 115 × 10[SUP-6]. The α″ ordering treatment resulted in a small decrease of saturation magnetostriction. Magnetostriction decreased to negligible or small negative levels after D0[SUB19] and L1[SUB2] ordering treatments. [ABSTRACT FROM AUTHOR]

The optical properties of the ordered defect compound CuIn[sub 5]Se[sub 8], which crystallizes in a hexagonal structure, have been studied by the absorption technique. The analysis of the data shows that the band gap energy E[sub G] varies from 1.23 to 1.13 eV between 10 and 300 K. It is found that the variation of E[sub G] with temperature is due to the contribution of both acoustic and optical phonons with a characteristic phonon energy of about 14 meV. The optical absorption coefficient just below the absorption edge varies exponentially with photon energy indicating the presence of Urbach’s tail. The phonon energy hν[sub p] associated with Urbach’s tail, which is found to be 53 meV, is higher than the highest optical phonon mode reported for this compound, which is about 29 meV. The origin of the additional energy is attributed to the contribution of localized modes produced by structural disorder of low energy formation. An empirical relation, also used earlier in the case of 1:1:2 and other ordered defect compounds of the 1:3:5 phases, explains very well the variation of Urbach’s energy with temperature. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Presents a study which examined the ordering and stability of lead[sub 1-x]europium[sub x]tellerium alloys. Use of transmission electron microscopy; Experimental details; Results and discussion.

Presents a study which examined the consequences for magnetism of icosahedral site symmetry and of long-range icosahedral ordering as found in quasicrystals. Factors that were predicted for long-range icosahedrally ordered magnets; Description of icosahedral quasicrystals; Reason for using the term quasicrystals; Examples of crystal structures that exist with local icosahedral structural units.

Examines γ-Fe[sub2]-O[sub3] particles by convergent beam electron diffraction to determine the crystal symmetry. Commercial samples obtained; Occurrence of order-disorder transition.

Reports on the effect of order-disorder transition on magnetic properties of high silicon-iron single crystals. Method used to make high-silicon single crystals; Way that can change the saturation magnetization, the magnetocrystalline anisotropy constant and the saturation magnetostriction constants in such crystals; Factor to which the phenomena is attributable.

Investigates the effects of growth rate on the step structure and ordering in gallium-indium-potassium (GaInP) epitaxial layers. Formation of copper-platinum (CuPt) ordering during epitaxial growth; Atomic-scale physical processes occurring on the surface; Correlation between step structure and ordering.

Presents information on a study which used surface photoabsorption measurements to clarify the copper-platinum ordering mechanism in Ga[sub0.5]In[sub0.5]P layers grown by organometallic vapor phase epitaxy. Methodology of the study; Results and discussion on the study; Conclusions.

Presents a study that investigated the effect of growth rate on step structure and ordering in gallium indium phosphide. Method of the study; Results and discussion; Conclusion.

The effects of ordering on the conductivity of carriers on a planar honeycomb lattice is studied using a modified Monte Carlo technique. The hopping model includes repulsion between carriers on nearest-neighbor sites. In agreement with previous work, we find an ordered region on the phase diagram for ion density ρ in the range 0.41≤ρ≤0.59 for sufficiently low temperatures. Within this composition range of the phase diagram, ordering effects on the conductivity and on its temperature dependence are very substantial; previous results which did not correctly include the ordering effects yield quite different conductivities. We also calculate correlation factors, diffusion coefficients, and several different kinds of order parameters. Experiments on systems such as Ba++ β‘-alumina and AgCrSe2 should be able to probe these ordered regions, and our results predict the influence of structure on the transport of the mobile ionic species in such compounds. [ABSTRACT FROM AUTHOR]

We extend to a new antiferromagnetic alloy, IrMn, point-contact based studies of the effect of a large current density on the exchange bias at antiferromagnet/ferromagnet (AFM/F) interfaces. Similarly to the case of AFM=CoFe, a negative current density ∼1012 A/m2 injected through the F=CoFe into an IrMn/CoFe interface was found to increase the exchange bias, while a positive current decreased it. The model used to describe the data for FeMn/CoFe, based on predicted current-induced torques on AFM, can explain the new data. [ABSTRACT FROM AUTHOR]

In this paper we examine the elastic (c′ and c44) and magnetostrictive (λ100 and λ111) behaviors of Fe100-xGex for 4

Planar patterned media using CrPt3 ordered alloy films were fabricated by Ar+ or Kr+ ion irradiation through nanoimprinted or electron beam lithography made masks. CrPt3 ordered alloy film on fused quartz substrate exhibits a large perpendicular anisotropy of 5×106 erg/cc and a large coercivity of 12 kOe, and we found that its magnetic order (magnetization) was completely suppressed by a quite low Ar+ or Kr+ ion dose of about 1–2×1014 ions/cm2. Magnetic force microscope image of the ion-beam patterned CrPt3 with a bit size of 90×90 nm showed clear magnetic contrast in nonirradiated regions, while no magnetic contrast in irradiated regions. The read-back waveform taken from an ion-beam patterned CrPt3 disk with 600 nm patterning pitch showed sharp signal transition between irradiated and nonirradiated regions, which indicates the possibility of high-density planar patterned media using CrPt3 ordered alloy. [ABSTRACT FROM AUTHOR]

Abstract We have investigated the effect of synthesis conditions of BCNO compounds on BN formation and its structural ordering. BCNO compounds were synthesized from boric acid (H 3 BO 3)-melamine (C 3 H 6 N 6) mixtures with various molar ratios (H 3 BO 3 :C 3 H 6 N 6 = 1:1 to 6:1) at 400 °C. The BCNO compounds were then subjected to post heating between 1400 °C and 1800 °C under argon flow. The final products were crystalline BN with hexagonal symmetry exhibiting varying degrees of structural ordering. As the H 3 BO 3 to C 3 H 6 N 6 ratio in the starting composition is increased, BN formation temperature decreases and the structural ordering of BN increases. Post heating at higher temperature also promotes BN formation and structural ordering. The findings indicate that synthesis and structural ordering of BN can be tailored by controlling starting composition and post heating temperature. These observations may provide a guideline to synthesize high or low-density polymorphs of BN at reduced pressure, temperature, or both. Graphical abstract Boron nitrides formed from BCNO compounds exhibited higher degree of structural ordering during post-heating when higher H 3 BO 3 to C 3 H 6 N 6 molar ratios were initially used to synthesize BCNOs. fx1 Highlights • Correlation between BCNO synthesis conditions&BN formation at high temperatures. • Increase in H 3 BO 3 :C 3 H 6 N 6 ratio promotes BN formation and its structural ordering. • Increase in post heating temperature promotes BN formation. • BN synthesis with varied 3-D structural ordering, particle size and morphologies. [ABSTRACT FROM AUTHOR]

Abstract To understand the mechanism of mass transfer during solid state reactions and order-disorder transitions the formation processes of CuAuI and L1 0 -FePd ordered structures at solid state reactions in Cu/Au и Fe/Pd bilayer thin films have been carried out using the method of in situ electron diffraction (ED). The value of the long-range order (LRO) parameter has been estimated for the L1 0 type ordered structures being formed; the order-disorder transition temperatures have been determined. The formation mechanism of the L1 0 type ordered structures formed at the initial stages of the solid state reaction in the Cu/Au and Fe/Pd thin films has been suggested. In the case of Cu/Au it has been shown that the interdiffusion of copper and gold at the initial stage of the solid state reaction results in the reduced size of the grains of the initial materials, as a result, nanocrystalites of the Cu-Au solid solution are formed, and further, grains of the CuAuI ordered solid solution appear and their growth begins. Graphical abstract fx1 Highlights • Solid state reactions in Cu/Au and Fe/Pd bilayer thin films have been investigated. • Structural phase transformations have been studied by in situ ED. • The formation processes of CuAuI and L1 0 -FePd ordered phases have been studied. • The value of the long-range order parameter has been estimated for the ordered structures. • The formation mechanism of the L1 0 type ordered structures has been suggested. [ABSTRACT FROM AUTHOR]

We calculate long-range interactions between Al-Y clusters along the stacking direction in Mg-Al-Y alloys with long-period stacking ordered (LPSO) structure by using first-principles calculation based on density functional theory (DFT). We find that the highly ordered LPSO structure, recently observed in Mg 75 Al 10 Y 15 alloy with 10H-type stacking sequence, is the most stable in thirteen polytypic structures. Relative energy differences in the thirteen polytypic structures suggest that significant long-range interactions between the separated stacking faults bring the highly ordered LPSO structure although short-range interactions are dominant for the stability of the alloy. In addition, we calculate and compare the long-range interactions for sixteen Mg-Metal (M)-Rare Earth (RE) alloys which have been experimentally observed to form the LPSO phase, and reveal that the long-range interactions in the alloys with M = Al are one digit larger than those with M = Zn. These results suggest that the long-range interactions between Al-RE clusters play an important role to form the highly ordered LPSO structure in Mg-Al-RE alloys. [ABSTRACT FROM AUTHOR]

A mean-field model based on the elasticity theory of point defects has been developed to investigate the role of uniform stress fields on the long-range ordering of carbon atoms in bct-iron. From an analysis of the thermodynamic equilibria, composition – temperature – stress state diagrams are derived. We demonstrate that ferrite, martensite and supercritical iron are various instances of the same bct-iron phase region. A coherent mapping of the phase transitions is drawn, identifying (i) continuous transitions such as ferrite ordering, martensite enhanced ordering and ferrite – martensite transformation, and (ii) discontinuous transitions such as temperature-induced martensite and stress-induced martensite. Our analysis is supported by rigid-lattice Monte Carlo simulations. Recently published experimental results on highly-drawn perlitic wires are re-interpreted in terms of supercritical iron, rather than strain-induced martensite. Novel low-temperature thermomechanical treatments of supersaturated ferrite are suggested, for improved nanostructure design of martensitic steels. [ABSTRACT FROM AUTHOR]

In order to identify the impact of the degree of Cu–Zn order in kesterite Cu2ZnSn(S,Se)4 solar cell absorbers on defect states and band tails, we perform photoluminescence (PL), photoluminescence excitation, and time-resolved photoluminescence (TRPL) spectroscopy. The PL lineshape and further PL characteristics such as state filling are analysed as a function of Cu–Zn order. Furthermore, TRPL decays and band tails are quantified. No significant modification in the defect states is caused by changes in Cu–Zn order, meaning that the formation of the defect states is not mainly determined by disorder in the Cu–Zn plane. In regard to band tailing, a small tendency to a decrease in the tailing parameter for the states with a high degree of Cu–Zn order compared to states with a low degree of Cu–Zn order is obvious. However, this reduction is small compared to the reduction of the defect density accompanied by the increase in the degree of Cu–Zn order. Hence, band tails are not mainly formed due to disorder in the Cu–Zn planes. [ABSTRACT FROM AUTHOR]

Co2−xMn1+xSi films with various composition x were epitaxially grown using molecular beam epitaxy (MBE). High crystallinity and atomic ordering in the prepared Co2−xMn1+xSi films were observed, and their magnetic damping and anisotropic magnetoresistance (AMR) effect were systematically investigated. An ultra-low magnetic damping constant of 0.0007 was obtained in the Co2−xMn1+xSi film with a valence electron number (NV) of about 29.0. Additionally, a relatively large negative AMR effect was observed in the Co2−xMn1+xSi films that had a NV of about 29.0. This low damping and the large negative AMR effect indicate that epitaxial Co2−xMn1+xSi films with high atomic ordering grown by MBE possess a high-spin polarization. [ABSTRACT FROM AUTHOR]

The order-disorder transition produced by ball milling in the intermetallic Fe[SUB70]Al[SUB30] has been systematically studied by x-ray diffraction, calorimetry, and Mössbauer experiments. These techniques show a monotonous transformation that ends after 6 h of milling. In the transition, the lattice parameter increase amounts to 0.7% and there is a large enhancement of the alloy's magnetism. [ABSTRACT FROM AUTHOR]

The combination of Mössbauer spectroscopy and magnetization measurements is demonstrated to be efficient in the determination of the phases responsible for the glassy magnetic dynamics of the highly disordered alloy Fe[sub 35]Al[sub 50]B[sub 15] produced by mechanical alloying. Its spin-glass behavior is apparent from the FC-ZFC magnetization irreversibility, the thermoremanent magnetization, and the slightly frequency-dependent peak in the temperature dependence of the ac susceptibility. Furthermore, the maximum at T[sub p] ≈ 22 K in the real component of the ac susceptibility is accompanied by a sudden onset of the imaginary component. The fit of the frequency dependence of T[sub p] to the critical slowing down law yielded a critical exponent z v = 8 ± 1. However, Mössbauer spectroscopy uncovered the existence of two different Fe environments, of which only the minor one freezes at low temperatures into a distribution of magnetic sextets. This result, combined with the superparamagnetic behavior detected at moderate fields, allowed us to ascribe the spin glass behavior to the presence of interacting, very fine, ferromagnetic clusters (estimated size ∼ 1 nm). The origin of this nanoscale compositional heterogeneity is argued to be related to regions of partially unalloyed Fe. The conclusions are contrasted with other mechanically alloyed systems with reported spin glass behavior or compositional inhomogeneity. [ABSTRACT FROM AUTHOR]

Magnetization vs temperature behavior of RuSr[sub 2]GdCu[sub 2]O[sub 8-δ] (Ru-1212) measured in an field of 5 Oe, shows a clear branching of zero-field-cooled (ZFC) and field-cooled (FC) curves around 140 K, a cusp at 135 K, and a diamagnetic transition around 20 K (in the ZFC branch). The cusp at 135 K is due to the antiferromagnetic ordering of the Ru moments. The magnetization-field isotherms, below 50 K, show a nonlinear contribution from a ferromagnetic component. The resistance vs temperature behavior of the compound, in applied fields of 0, 3, and 7 T, confirms that the sample is superconducting at around 20 K. The superconducting transition exhibits field broadening of a type different than that known for conventional high T[sub c] superconductors. The magnetoresistance (MR) is negative above the Ru magnetic ordering temperature of 135 K, while below this temperature, MR displays a positive peak in low fields and becomes negative in higher fields. A maximum of 2% is observed for the negative MR value at the Ru magnetic ordering temperature. An electron diffraction pattern obtained for this Ru-1212 sample shows two types of superstructure; one with a weak spot at the center of the a-b rectangle and the other only along the b direction. It is possible that either Ru/Cu or Ru[sup 4+] / Ru[sup 5+] ordering of 2b periodicity takes place along the b direction. [ABSTRACT FROM AUTHOR]

Atomic ordering, nanostructure and the magnetic properties of polycrystalline FePdPt thin films deposited with MgO underlayers have been investigated. The film thickness was fixed at 5 nm in all films, a thickness where perpendicular anisotropy is dominant. Films deposited at ambient temperature were postannealed at various temperatures to study the kinetics of atomic ordering. The Pd additions to FePt were effective in reducing the temperature needed for atomic ordering. The mean grain size determined by transmission electron microscopy is about 10 nm in annealed films. Within the limits of our observations, FePdPt films do not show phase separation into more than one phase of the L 10 structure. The maximum coercivity (H[sub c]) for annealed FePdPt films is about ∼3000-4000 Oe. In situ ordered FePdPt films at 530 °C show no indication of a lower temperature for atomic ordering. [ABSTRACT FROM AUTHOR]

The influences of random disorder in the barrier on tunnel conductance (TC) and magnetoresistance (TMR) in ferromagnet (FM)/insulator (semiconductor) (I(S))/FM junctions are investigated theoretically taking into account spin-orbit (SO) interaction. The TMR decreases significantly due to the spin-flip scattering (SF) caused by the SO interaction. We have found that the SF scattering is much stronger for anti-parallel configuration of magnetization and the TMR can even be inverted when the SF scattering is beyond some critical value. The numerical calculations are performed within the single-orbital tight-binding model using the recursive Green's function method based on the extended Landauer-Bfittiker formula. [ABSTRACT FROM AUTHOR]

Current–voltage (I–V) characteristics of Pr[sub 0.5]Sr[sub 0.3]Ca[sub 0.2]MnO[sub 3] are measured at different temperatures and different fields. Our data of I–V curves show a crossover from linear to nonlinear behavior at the temperature lower than the charge ordering temperature. New findings in this work include (i) abrupt jumps/drops of voltage in each I–V curve below 100 K and (ii) an enhancement of magnetoresistance (MR) ratio from 15% to 20% which is associated with the unusual voltage jumps/drops in I–V curves. The enhancement of MR ratio evidences the existence of an intermediate state between the charge ordering state and the charge ordering breakdown state. Most importantly, the existence of such intermediate state provides a new route to achieve a low field colossal magnetoresistance for future applications of spintronics. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Single crystals of R[sub 1/3]Sr[sub 2/3]FeO[sub 3] (R=Pr, Nd, and Sm) were synthesized by the floating zone method and their magnetic properties and charge ordering (CO) transition related to lattice dynamics were systematically investigated. Mo¨ssbauer spectra of R[sub 1/3]Sr[sub 2/3]FeO[sub 3] were taken at various temperatures ranging from 12 K to room temperature. The charge disproportionation in Pr[sub 1/3]Sr[sub 2/3]FeO[sub 3] was detected below 190 K, in which two kinds of iron with valence states Fe[sup 3+] and Fe[sup 5+] were found with ratio of 2:1. The iron with valence state Fe[sup 4+] in Pr[sub 1/3]Sr[sub 2/3]FeO[sub 3] coexists at and above 150 K, and its ratio increased from 13% to 66% as the temperature rose. The (Nd[sub 1-y]Sm[sub y])[sub 1/3]Sr[sub 2/3]FeO[sub 3] (y=0.0, 0.2, 0.4, 0.6, and 0.8) with least lattice distortion underwent a CO phase transition at and below T[sub CO]=163 K and accompanying the charge disproportionation into nominally Fe[sup 3+] and Fe[sup 5+] sites as well as a canted antiferromagnetic spin ordering. In this charge ordering state, a sequence of Fe[sup +3]Fe[sup +3]Fe[sup +5]Fe[sup +3]Fe[sup +3]Fe[sup +5] exists aligned along the [111] direction of the pseudocubic perovskite structure. In this study, the CO at x=2/3 disappeared in the case of R=Sm. Indeed, disappearance of the CO transition was detected by systematic decrease of a spontaneous magnetization with increase of y in the system of (Nd[sub 1-y]Sm[sub y])[sub 1/3]Sr[sub 2/3]FeO[sub 3]. This result shows that the charge ordering state was realized with strong hybridization between the Fe and O atoms. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The magnetic ordering in the series of transition metal alloys (Fe[sub 1-x]T[sub x])[sub 3]Ga[sub 4] with T=Ni and Ti having values of x in the range 0.05≤x≤0.20 has been investigated at high fields and low temperatures. Magnetization measurements revealed that in contrast to other T substitutions, Ni and Ti induce completely different types of effects on the magnetic properties. In the case of Ni substitution a ferrimagnetic-like type of magnetic order is induced at low compositions and low temperatures and Ti produces a ferromagnetic ground state. For Ti alloys with low composition as the temperature is increased a field induced transition starts to appear at about 50 K which persists up to room temperature suggesting a phase transition from a ferromagnetic to an antiferromagnetic state. The phase diagrams of the Ni and Ti system are explainable in terms of the Moriya-Usami and Isoda theories. Preliminary neutron diffraction measurements on the Ni alloys carried out at ILL suggest the existence of short-range order over a certain temperature range. The behavior observed so far on the various substituted systems leads us to believe that there is a clear relation between the magnetic properties and the relative position of the substitution element with respect to Fe in the Periodic Table. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Rapidly solidified Sm[sub 11]Fe[sub 89] was observed to form partially ordered Sm[sub 2]Fe[sub 17]. The ordering increased systematically with annealing temperature, reaching an order parameter of 0.8 after annealing at 950 °C for 15 min. The coercivity of the corresponding interstitial compound Sm[sub 2]Fe[sub 17]N[sub x] varied with annealing temperature and thus order parameter. The coercivity reached a maximum for an order parameter of 0.45–5, then dramatically decreased as the order increased. This behavior is characteristic of demagnetization controlled by domain wall pinning by antiphase boundaries. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The effect of nitrogen incorporation on the L 1 0 ordering transformation of CoPt thin films deposited by dc magnetron sputtering on MgO substrate with/without TiN seed layers has been investigated. Without TiN seed layer, CoPt film is subjected to a tensile stress, and the perpendicular magnetic anisotropy (PMA) decreases with N 2 gas flow ratio. This is due to the degradation of tensile stress, which is proven to be beneficial to the ordering transformation of L 1 0 CoPt. On the contrary, when sputtered on TiN seed layer, CoPt film is subjected to a compressive stress and the PMA increases with N 2 gas flow ratio. The increase of PMA is due to the increase in equilibrium vacancy concentration, which also promotes the diffusion of Co and Pt atoms during annealing. On quartz substrate, the maximum perpendicular coercivity of 11 kOe was obtained at the CoPt/TiN bilayer films with 50% partial N 2 gas flow ratio after post annealing at 700 °C. By partially flowing nitrogen during the deposition, a 200 °C reduction of ordering temperature was also obtained. [ABSTRACT FROM AUTHOR]

A series of quaternary Heusler alloys NiCuMnZ (Z = In, Sn, Sb) have been prepared experimentally. Their structural and magnetic properties have been investigated by XRD, magnetic measurements and first-principles calculations. NiCuMnZ all crystallize in a cubic Heusler structure. But the atomic ordering in them is different and related to the main group element Z. NiCuMnSb is highly ordered while NiCuMnIn and NiCuMnSn have a degree of Cu-Mn disorder in the lattice. In these alloys, Cu atom has strong preference for the B (0.25, 0.25, 0.25) site, though Cu has more valence electrons than Mn and Ni. The saturation magnetization M s at 5 K is 3.99μ B /f.u., 4.20μ B /f.u. and 4.02μ B /f.u. for NiCuMnSb, NiCuMnSn and NiCuMnIn, respectively. First-principles calculations suggest that the large total moments mainly come from the contribution of Mn. The T C decreases rapidly from 716 K in NiCuMnSb to 340 K in NiCuMnIn, relating to the increasing degree of atomic disorder in their lattice. But the partial moments of Mn are always in ferromagnetic coupling though they are nearest neighbors in partly disordered NiCuMnSn and NiCuMnIn. [ABSTRACT FROM AUTHOR]

Magnetic properties of the Ce 2 Rh 3 Ge compound are studied by combined investigations involving magnetization and susceptibility measurements, electron microscopy with energy dispersive analysis, X-ray photoelectron spectroscopy (XPS) as well as band structure calculations. Our calculations well agree with the experimental XPS data and predict non-magnetic ground state for the Ce 2 Rh 3 Ge. We attribute the previously reported weak magnetic ordering in the Ce 2 Rh 3 Ge to the presence of the magnetic impurity phase composed mainly from the Ce 5 RhGe 2 . The amount of the impurity phase determined from structural investigations explains quantitatively magnetic properties published in previous reports. The magnetic ground state of Ce 5 RhGe 2 phase was determined from the DFT based calculations. [ABSTRACT FROM AUTHOR]

We identified new magic compositions of Pd-Au nanolloys of simple symmetries according to the icosahedral and the cubic truncated octahedral structures. Chemically ordered structures as well as segregated ones are characterized using Monte Carlo simulations in semi-grand canonical ensemble and tight-binding semi-empirical potential fitted to ab initio calculations for the Pd-Au system. Ordering and surface (or core) segregation phenomena can be distinguished by their behavior as a function of the temperature: chemical ordering at surface or in the core disappears above a critical temperature (which is lower or equal to the bulk alloy order-disorder temperature), whereas surface/core segregation (core-shell structures) remains at high temperature, although the interfacial profile is less abrupt. [ABSTRACT FROM AUTHOR]

Fe-Mn-Al-C steels are promising materials to design lighter automotive safety parts. It has been shown experimentally that upon cooling, high temperature austenite decomposes into low temperature austenite and kappa carbides via spinodal decomposition and ordering process. In this paper, a mean-field model at the atomic scale designed to simulate the formation of kappa-carbides is proposed. The first results obtained prove the ability of the model to reproduce several experimental observations such as the L1 2 ordering of the disordered FCC, the E2 1 ordering of C atoms leading to the formation of the κ-phase or the partition of C atoms between disordered FCC and the L1 2 phase during the spinodal decomposition. [ABSTRACT FROM AUTHOR]

Focuses on a study that examined the behaviors of ordering and disordering in binary iron-aluminum thin films. Manner of examining Fe[sub3]Al films; Composition of the films.

Presents a study which examined the oxygen dependence of the magnetic order of neodymium in neodymium barium[sub2]copper[sub3]oxygen[sub6+x]. Details of neutron scattering experiments; Discussion of specific heat measurements; Results.

Discusses a study which examined the short-ordering of frustrated magnet compound Tb[sub2]Mo[sub2]O[sub7]. Structure of the magnetic compound; Determination of the nature of magnetic ordering in the compound; Analysis of small-angle neutron scattering.

Presents a study which examined the quenching of ferrimagnetic-like ordering in strontium chromium[sub8]iron[sub4]oxygen[sub19] hexagonal ferrite. Experimental procedure; Results; discussion.

Presents a study which examined the magnetic states of disordered nickel-manganese alloys under hydrostatic pressure. Measurement of low-field alternating current susceptibility of disordered nickel-manganese alloys; Experimental procedure and data; Results and discussion.

The microstructure and ordering are studied in gold-base alloys ZlM-80 and ZlKh-05 for low-level slide contacts. It is shown that heating in the range of 300 - 500°C may cause long-range ordering, fragmentation and recrystallization of the alloys. [ABSTRACT FROM AUTHOR]