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Manipulation of topological structures has become one of the most interesting topics in ferroelectrics through multiple excitations due to their prospective applications in electro-mechanical-optic devices. Scanning probe microscopy (SPM) has been developed as a powerful tool to manipulate the polar state in ferroic materials, in which the electric field induced by charged SPM enables dynamic coupling between the switching of the polar states and electromigration of oxygen vacancies, resulting in unknown influences of oxygen vacancy on the polar state in ferroelectric topological structures. Here, we regulate the polar state by considering oxygen vacancies and a non-uniform electric field under the charged SPM experiment for flux-closure domain structures in PbTiO3 thin films. The charged SPM probe can excite the growth of newly flux-closure domains to improve the density of topological states. In contrast, oxygen vacancies are found to suddenly prohibit the evolution of the flux-closure domain structure, when their concentration jumps to a threshold value. Our results might give guidelines to increase and stabilize the memory unit through co-modulating the electric field and ions injection in the information field. [ABSTRACT FROM AUTHOR]

We investigate the frequency dispersion of complex permeability in the GHz range in superparamagnetic nickel–zinc ferrite thin films with different Ni/Zn ratios using a microstrip probe. The films, comprising crystallites as small as 3 nm and deposited by a microwave-irradiation-assisted solvothermal method, exhibit the coexistence of two resonance characteristics—a ferromagnetic resonance peak ( f r ) at ∼2 GHz and a superparamagnetic resonance peak ( f b ) above 20 GHz, breaching Snoek's limit. The high value of f r is attributed to the high surface anisotropy and far-from-equilibrium distribution of cations in the lattice, while f b is attributed to the thermally driven superparamagnetic relaxation of ferrite nanocrystallites in the thin films. This work demonstrates the feasibility of employing superparamagnetic ferrite thin films so deposited as excellent CMOS-integrable magnetic components for high-speed and high-frequency electromagnetic device applications. [ABSTRACT FROM AUTHOR]

The advent of modern thin-film deposition approaches has ushered in a new era of designed materials with well-controlled composition distributions, e.g., compositionally graded ferroelectric (CGFE) thin films, and thereby, it is readily accessible CGFE/FM (ferromagnetic) multilayer thin films. Being recognized this emerging class of materials, in this study, we develop a phase-field model based on the Ginzburg–Landau theory that takes into account the gradient of ferroelectric (FE) compositions in order to predict material properties of CGFE/FM thin films. The developed phase-field model is applied to investigate the effect of the FE composition gradient on magnetoelectric (ME) coupling of graded Pb(1−x)SrxTiO3/CoFe2O4 laminated nanocomposites. Two types of composition gradients are considered: inward (O-type) and outward (X-type) gradients. Unusual polarization domain structures with curved domain walls are formed in CGFE layers, which are governed by the composition gradients and distinct from typical stripe domains in homogeneous counterparts. As a result, the ME effect is strongly dependent on the composition gradient. Particularly, the ME coupling in the O-type nanocomposites increases with the increasing composition gradient, while it decreases in the X-type ones. The dependence of ME coupling on the composition gradient originates from the distinguishable energy distributions in O-type and X-type nanocomposites. This work, therefore, provides a strategy to design the ME effect via the configuration of the composition gradient. [ABSTRACT FROM AUTHOR]

This paper describes our proposed measurement technique for the magnetization dynamics in thin films, which employs a microstripe line probe to detect ferromagnetic resonance (FMR) spectra for a film sample either with or without tensile stress. By measurement of FMR frequency shifts using Lorentzian fits to the FMR spectra for a film with and without tensile stress, saturation magnetostriction (λs) can be determined. The measured values were compared with those estimated by the optical cantilever method using the same samples in good agreement. At the same time, a Gilbert damping constant (α) was determined using both the FMR frequency and the FMR linewidth for the tensile stress free film. The results of the experiment demonstrate that our proposed measurement technique allows for more precise evaluation of magnetization dynamics by providing information on both α and λs simultaneously for an individual sample. [ABSTRACT FROM AUTHOR]

Partially ordered Fe-N thin films were grown by a facing target sputtering process on the surface of a (001) Ag underlayer on MgO substrates. It was confirmed by x-ray diffraction that the Ag layer enlarged the in-plane lattice of the Fe-N thin films. Domains of the ordered α″-Fe16N2 phase within an epitaxial (001) α′-FexN phase were identified by electron diffraction and high-resolution aberration-corrected scanning transmission electron microscopy (STEM) methods. STEM dark-field and bright-field images showed the fully ordered structure of the α″-Fe16N2 at the atomic column level. High saturation magnetization(Ms) of 1890 emu/cc was obtained for α″-Fe16N2 on the Ag underlayer, while only 1500 emu/cc was measured for Fe-N on the Fe underlayer. The results are likely due to a tensile strain induced in the α″-Fe16N2 phase by the Ag structure at the interface. [ABSTRACT FROM AUTHOR]

We performed electrical transport measurements on α-sexithiophene crystalline grains using a dual-probe atomic force microscopy system having two independently controlled cantilever probes. The field-effect transistor characteristics were measured by varying the distances between the two probes brought in contact with the surface of the grains. It was clearly shown by the transfer line method that the grain boundary is the dominant factor limiting the electrical properties of organic thin films. Moreover, the hole transport across the grain boundary was found to be more affected by the oxygen hole doping than that within the crystalline grain. [ABSTRACT FROM AUTHOR]

We investigate the ferromagnetic resonance response of palladium-cobalt bi-layer thin films to hydrogen charging at atmospheric pressure. We find that hydrogen absorption by the palladium capping layer results in the narrowing and shifting of the ferromagnetic resonance line of the underlying cobalt. We explain the observed phenomena as originating from reduction in the spin pumping effect and from variation in the magnetic anisotropy of the cobalt layer through an interface effect. The shift of the resonance frequency or field is the easiest to detect. We utilize this to demonstrate functionality of the bi-layer film as a hydrogen sensor. [ABSTRACT FROM AUTHOR]

The elastic stiffness of epitaxial and polycrystalline L10 FePt films is studied by picosecond ultrasonics coupled with x-ray reflectivity analysis, and we find that C33 of L10 FePt is 309 GPa. The morphology of FePt films shows dependence on the film thickness; as the film thickness increases the mazelike structure changes to a continuous film. The elastic stiffness correlates with the morphology change, and it increases as the film thickness increases. When the film thickness exceeds 40 nm, the elastic stiffness becomes independent of the film thickness, and we define the saturated value as C33 of L10 FePt. [ABSTRACT FROM AUTHOR]

This paper focuses on the structure of nanoporous SiOCH thin films deposited using a porogen approach by plasma enhanced chemical vapor deposition (PECVD). The grazing incidence small angle x-ray scattering signal demonstrates the existence of a biphase pattern in hybrid films, deposited by PECVD. After porogen removal, there are few differences between pore pattern of optimized ultraviolet (UV) illuminated and thermally treated samples: anisotropy of the pore pattern is observed in both samples, probably due to the porogen degradation. Finally, a kinetic study of porogen degradation by UV shows that the porous structure develops in only a few minutes. [ABSTRACT FROM AUTHOR]

We developed a nanoscale orientation template for quasisingle crystalline epitaxial growth of thin film phase pentacene. By using [formula] Bi termination of surface dangling bonds on step-bunched vicinal surface of Si(111), thin film phase epitaxial pentacene was grown with the crystal axes aligned to the surface steps. Alignment occurred when the step height was higher than the molecular height. The mechanism of the alignment was examined by calculating the energy of the crystal edge. [ABSTRACT FROM AUTHOR]

The authors investigate the magnetooptical and magnetotransport properties of Mn-doped amorphous Ge (a-Ge1-xMnx) thin films deposited on thermally oxidized Si substrates. Magnetic circular dichroism measurements reveal that their ferromagnetic ordering appears for x>0.02 and the films show magnetically homogeneous behavior. The resistivity of the films decreases with increasing x, and the temperature dependence of the resistivity shows semiconductor-like behavior. The anomalous Hall effect of the a-Ge1-xMnx films also exhibits ferromagnetic behavior. The temperature dependence of magnetization is consistent with that of the magnetooptical and magnetotransport results. These results indicate that the a-Ge1-xMnx films behave as a ferromagnetic semiconductor. [ABSTRACT FROM AUTHOR]

We report the effect of epitaxial growth and lattice mismatch on the enhancement of saturation magnetization (Ms) of ferromagnetic γ′-Fe4N thin films deposited on different single crystal substrates having lattice mismatches from 0% to 11%. It was found that Ms in the γ′-Fe4N film increased with increasing degree of epitaxy and minimizing lattice mismatch between the film and the substrate. Maximum saturation magnetization of 1980±20 emu/cm3 (about 24% higher than previous result) was obtained with LaAlO3(100) substrate having zero lattice mismatch after postannealing of 30 min, which is believed to originate from magnetovolume effect in well-ordered epitaxially grown films. [ABSTRACT FROM AUTHOR]

Strong dependence of surface residence time of a planar organic molecule (hydrogen phthalocyanine) on vicinal surfaces of hydrogen-terminated Si(111) was observed in pulsed molecular beam scattering experiments. These results can be explained by the difference in the microscopic contact area of the molecules on the surface, which determines the binding force between the migrating molecules and the surface. The relationship between the observed behavior and the organic thin film growth is discussed. [ABSTRACT FROM AUTHOR]

We have studied L10-FePt thin films with a Bi underlayer. Experimental results show that the ordering temperature of the L10-FePt film can be lowered down to 300–350 °C and the in-plane coercivity HC of the film is obviously enhanced by introduction of a Bi underlayer. After annealing at 400 °C for 20 min, a Bi/FePt film realizes a HC of 13.5 kOe and the ratio of the remnant magnetization Mr to the saturation one MS of as high as 0.93. The reduction of the ordering temperature and the enhanced magnetic properties of L10-FePt films can be understood by considering the large diffusivities of Fe and Pt associated with Bi diffusion. [ABSTRACT FROM AUTHOR]

We have studied the magnetic and structural properties of AuCu(0–50 nm)/FePt(2–50 nm) films after annealing at various temperatures. The results indicate that, by introducing a thin equiatomic AuCu underlayer, the ordering temperature of FePt films with thickness even down to 5 nm can be significantly reduced to 350 °C, at which a large coercivity is developed. In fact, the coercivity is as high as 4.6 kOe for a 5 nm FePt film on a 10 nm AuCu underlayer after annealing at 350 °C and this value is raised up to 7.5 kOe when annealed at 400 °C, while the corresponding sample without a AuCu underlayer has to be annealed at a temperature beyond 600 °C in order to achieve a coercivity of 4 kOe. The ordering of the thin AuCu film at relatively low temperature and thus coherently inducing the ordering of FePt film led to the formation of the ordered FePt phase at a much lowered temperature. [ABSTRACT FROM AUTHOR]

Phase separation of Co-W sputtered thin films having a large magnetocrystalline anisotropy energy have been investigated. A nanoscale compositional fluctuation caused by magnetically induced phase separation was directly confirmed in the films deposited on a heated substrate in analogy with Co-Cr-based alloys. The difference between the phase separation features in Co-W and Co-Cr is attributed to the difference in their elastic energy It is expected that the phase separation is enhanced by selecting optimum sputtering conditions. The Co-W system, therefore, is considered to be a promising candidate as a base alloy system for high-density recording media. [ABSTRACT FROM AUTHOR]

Effect of magnetic field annealing on chemical ordering of FePt films has been investigated. It is found that the ordering rate in FePt films is enhanced by applying a magnetic field during postdeposition annealing. Measurements of the structure and magnetic properties of FePt films reveal that the disorder-order transformation starts at or below 450°C when the film is annealed in a magnetic field of 40 kOe. The possible reason for the enhancement in the ordering of FePt films by magnetic field annealing is discussed. [ABSTRACT FROM AUTHOR]

We have investigated carrier transport in a crystalline oxide semiconductor InGaO3(ZnO)5 using single-crystalline thin films. When carrier concentration is less than 2×1018 cm-3, logarithm of electrical conductivity decreases in proportion to T -1/4 and room-temperature Hall mobility was as low as ∼1 cm2(V s)-1. When carrier concentration was increased to 4×1018 cm-3, the conduction mechanism changed to degenerate conduction and room-temperature Hall mobility was steeply increased to >10 cm2(Vs)-1, showing metal–insulator transition behavior. These results are explained by percolation conduction over distribution of potential barriers formed around conduction band edge. The potential distribution is a consequence of potential modulation originating from random distribution of Ga3+ and Zn2+ ions in the crystal structure of InGaO3(ZnO)5. [ABSTRACT FROM AUTHOR]

We have investigated the effect of extensive compositional change on the structure and magnetic properties of FePt sputtered films deposited at a substrate temperature of 300 °C. The Fe concentration in the FePt films was varied from 19 to 68 at. %. In the x-ray diffraction patterns, (001) and (003) superlattice peaks were observed at a Pt-rich composition range, indicating the formation of a L1[sub 0] ordered structure. A L1[sub 0] ordered Fe[sub 38]Pt[sub 62] film exhibited perpendicular magnetization with a large uniaxial magnetic anisotropy of K[sub u] = 1.8 × 10[sup 7] erg/cm³. [ABSTRACT FROM AUTHOR]

A local structural transition in heavily Fe-doped GaN films related to the magnetic properties has been revealed by fluorescence x-ray absorption fine structure (XAFS) analysis. The structural transition is explained (or considered to be induced) by the change in the degree of hybridization between Fe 3d and N 2p states, which can be evaluated by x-ray absorption near edge structure spectra. The XAFS analysis indicates that the present diluted magnetic semiconductor based on GaN can be fabricated by electron cyclotron resonance microwave plasma-assisted low-temperature molecular-beam epitaxy. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Examines the template effects in molecular beam epitaxy of ferromagnetic manganese arsenide (MnAs) thin films on (001) gallium arsenide (GaAs) substrates. Details on the growth and magnetization directions of the films; Effects of Mn monolayer deposition on GaAs substrate; Importance of first monolayers for epitaxial orientation.

We report a direct observation of giant saturation magnetization in Fe16N2. By exploiting thin film epitaxy, which provides controlled biaxial stress to create lattice distortion, we demonstrate that giant magnetism can be established in Fe16N2 thin film coherently grown on MgO (001) substrate. Explored by polarized neutron reflectometry, the depth-dependent saturation magnetic induction (Bs) of epitaxial Fe16N2 thin films is visualized, which reveals a strong correlation with the in-plane lattice parameter and tensile strain developed at near substrate interface. With controlled growth process and dimension adjustment, the Bs of these films can be modulated over a broad range, from ∼2.1 Tesla (T) (normal Bs) up to ∼3.1 T (giant Bs). [ABSTRACT FROM AUTHOR]

We have investigated the effects of B and C on the ordering of L1[sub 0]-CoPt films and confirmed the following quite different role between B and C in CoPt. A small amount of B considerably decreases the temperature for ordering and is interstitially incorporated into L1[sub 0]-CoPt along its c axis due to the large negative heat of solutions with Co and Pt. X-ray photoelectron spectroscopy analyses have revealed that B atoms combine with Co and Pt. In contrast, C is not incorporated into the CoPt lattice due to its positive heat of solution, resulting in no decrease in the ordering temperature. The present results reveal that CoPt films containing a small amount of B are promising for high density recording media. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

We have studied the chemical ordering of granular films (CoPt)[sub 1-x]Ag[sub x]/SiO[sub 2] with the concentration x=2-6 at. %. It was found that the additive Ag efficiently promotes the ordering process, reducing the ordering temperature by 100 °C compared with that of without Ag. The additive Ag also stimulates nearly perfect (001) orientation of the CoPt-ordered grains in the films with a thickness of less than 50 nm, resulting in a large perpendicular magnetic anisotropy. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]