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The voltage-controlled magnetic anisotropy of various magnetic materials is an effective method to realize the electronic devices with low power consumption. Here, we investigated the magnetic properties in Co2MnAl/GaAs heterostructures controlled by piezo voltages-induced strain using the magneto-optical Kerr effect microscopy. The coexistence of the in-plane cubic and uniaxial magnetic anisotropies was observed in the initial state of Co2MnAl thin films. The magnetic anisotropy was manipulated effectively by the piezo voltages. The two-step magnetic hysteresis loop measured along the [1−10] direction was changed into a square loop when the piezo voltage was −30 V (compressed state). On the contrary, the loop of the [110] direction was changed into a two-step loop. The loops of [100] and [010] axes represented the hard axes and were almost unchanged with the piezo voltages. We found that the transformations of loops in [110] and [1−10] axes were manipulated by the piezo voltage induced additional uniaxial anisotropy. Finally, we demonstrated that the planar Hall resistance (R H) in the Hall device can be effectively controlled by the piezo voltages. Our study identified that the voltage controlled room temperature magnetic devices through strain engineering could have great potential for spintronic applications. [ABSTRACT FROM AUTHOR]

We report the elastically induced magnetic phase transition of FeRh thin films on BaTiO3 (001) at the successive phase transitions of BaTiO3, which is accompanied by abrupt variations of magnetization and resistance of FeRh at saturated magnetic fields. In-situ X-ray diffraction at different temperatures reveal that the compressive strains are induced accompanied by the tetragonal to orthorhombic and the orthorhombic to rhombohedral structural phase transition of BaTiO3 during cooling, due to the changes in the lattice constant and domain structure in different phases. The compressive strain further stabilizes the antiferromagnetic phase of FeRh and accounts for the magnetization and resistance changes. [ABSTRACT FROM AUTHOR]

In this paper, we report on the microstructural and magnetic properties of CrxAl1-xN thin films with Cr concentrations ranging up to x=(8.5 ± 0.5) at. %. The thin films are sputter deposited on silicon substrates and exhibit a wurtzite type microstructure verified by X-ray diffraction measurements. A vibrating sample magnetometer based measurement equipment is used to investigate magnetic properties of the Cr doped thin films in a temperature range of T=10 K-300 K, revealing a paramagnetic behavior. With increasing temperature, the temperature independent diamagnetic contribution of the substrate material dominates the overall response characteristics. No room temperature ferromagnetism is observed for all samples investigated. [ABSTRACT FROM AUTHOR]

The magnetophoresis of water-suspended 4 μm-diameter superparamagnetic beads above topographically patterned, sputter deposited Ti(4 nm)/Au(60 nm)/[Co(0.7 nm)/Au(1 nm)] × 3 multilayers with perpendicular magnetic anisotropy was investigated. The results impressively demonstrate that the magnetic stray field landscape above the stripe structure when superimposed with an external, slowly rotating, field enables the directed transport of magnetic beads across the stripe panel with velocities up to 12 μm s-1. [ABSTRACT FROM AUTHOR]

Mg doped (Pb0.35Sr0.65)TiO3 (PST) thin films were fabricated on indium tin oxide /glass substrates by the sol–gel technique. The formation of the PST phase and control of the magnesium doping on the microstructure, defect states, and dielectric properties of the thin film were investigated by means of XRD, SEM, AFM, XPS, and impedance analysis. Results showed that the oxygen vacancies and the associated Ti3+ ions formed as V••o∼Ti′Ti dipole pairs, and the dipole pairs were aligned opposite to the direction of the intrinsic dipole moments in the PST thin film. The amount of dipole pairs was strongly affected by the formed Mg″Ti in the thin film. The minimum amount of the dipole pairs appeared in the PST thin film with Mg doping content of 6% in molar ratio. The thin film with Mg doping content of 6% showed high permittivity due to low offset from V••o∼Ti′Ti dipole pairs and low dielectric loss due to low defect electrons generated in the thin film simultaneously. The formed Mg″Ti in the oxygen octahedral contributed lower response of the dipole moments to external electric field and resulted in lower tunability of the PST thin film with increasing Mg doping content. Controlled by the substitution of Mg2+ ions for Ti4+ ions and the induced V••O∼Ti′Ti dipole pairs, the optimal figure of merit was obtained in the PST thin film with Mg doping content of 6% with which the thin film possessed the smallest dielectric loss and still high tunability simultaneously. [ABSTRACT FROM AUTHOR]

Stress is inevitable during thin film growth. It is demonstrated here that the growth stress has a significant effect on the dielectric constant of high-k thin films. ZrO2 thin films were deposited on Ge by reactive direct current sputtering. Stress in these films was measured using in-situ curvature measurement tool. The growth stress was tuned from -2.8 to 0.1 GPa by controlling deposition rate. Dielectric permittivity of ZrO2 depends on temperature, phase, and stress. The correct combination of parameters—phase, texture, and stress—is shown to yield films with an equivalent oxide thickness of 8 Å. Growth stresses are shown to affect the dielectric constant both directly by affecting lattice parameter and indirectly through the effect on phase stability of ZrO2. [ABSTRACT FROM AUTHOR]

Epitaxial intrinsic and Fe-doped CoTiSb thin films with C1b structure were grown on MgO(100) substrates by magnetron sputtering. The semiconducting-like behavior in both intrinsic and Fe-doped thin films was demonstrated by temperature dependence of longitudinal resistivity. The Fe-doped CoTiSb films with a wide range of doping concentrations can maintain semiconducting-like and magnetic properties simultaneously, while the semiconducting behavior is weakening with the increasing Fe concentration. For 21 at.% Fe-doped film, low lattice magnetic moment (around 0.65 μB) and high resistivity (larger than 800 μΩcm) are beneficial to its application as a magnetic electrode in spintronic devices. Anomalous Hall effect of 21 at.% Fe-doped film was also investigated and its behaviors can be treated well by recent-reported anomalous Hall scaling including the contribution of spin-phonon skew scattering. [ABSTRACT FROM AUTHOR]

We report on the epitaxial growth and room-temperature ferromagnetic properties of MgO thin films deposited on hexagonal c-sapphire substrates by pulsed laser deposition. The epitaxial nature of the films has been confirmed by both θ-2θ and φ-scans of X-ray diffraction pattern. Even though bulk MgO is a nonmagnetic insulator, we have found that the MgO films exhibit ferromagnetism and hysteresis loops yielding a maximum saturation magnetization up to 17 emu/cc and large coercivity, Hc=1200 Oe. We have also found that the saturation magnetization gets enhanced and that the crystallization degraded with decreased growth temperature, suggesting that the origin of our magnetic coupling could be point defects manifested by the strain in the films. X-ray (θ-2θ) diffraction peak shift and strain analysis clearly support the presence of strain in films resulting from the presence of point defects. Based on careful investigations using secondary ion mass spectrometer and X-ray photoelectron spectroscopy studies, we have ruled out the possibility of the presence of any external magnetic impurities. We discuss the critical role of microstructural characteristics and associated strain on the physical properties of the MgO films and establish a correlation between defects and magnetic properties. [ABSTRACT FROM AUTHOR]

We study the relationship between long range order parameters and the magnetocrystalline anisotropy of off-stoichiometric D022 Mn2.36Ga (MnGa) epitaxial films grown on MgO (001) and SrTiO3 (STO) (001) single crystalline substrates. MnGa films deposited on MgO (001) show rather large irregular variation in magnetization with increasing substrate temperature in spite of the improved long range order of total atomic sites. The specific site long range order of Mn-I site characterized in the [101] orientation revealed the fluctuation of the occupation fraction of two Mn atomic sites with elevated substrate temperature, which appears more relevant to the observed magnetization change than the long range order of the total atomic sites. In case of MnGa films grown on the lattice-matched STO (001), high long range order of the total atomic sites in spite of the existence of secondary phase represents that the lattice mismatch plays a crucial role in determining the atomic arrangement of Mn and Ga atoms in the off-stoichiometric compositional case of MnGa. [ABSTRACT FROM AUTHOR]

In this work, the transverse force-frequency sensitivity of magnetostrictive Metglas® (Fe85B5Si10) thin film coated AT-cut thickness shear mode quartz thin plate microresonator (500?μm × 500?μm × 19?μm) is experimentally measured and modeled in Lagrangian formulation by coupling magnetostrictive deformation equations with the basic plate equations from the theory of small deformation. The quartz plate resonator is fabricated by micromachining techniques and released into fixed-free structure using focused ion beam milling. Application of a magnetic field results in the out-of-plane bending of the structure due to elastic coupling between the magnetostrictive Metglas® and quartz resonator layers. As a result of the transverse loading and out-of-plane bending, the admittance characteristics of the resonator shifts, and these shifts are recorded in real time utilizing a network analyzer. The sensitivity is experimentally measured to be 162.3 mdeg/Oe for phase, corresponding to a frequency sensitivity of Δf/H ?=?11?Hz/Oe. The equivalent force-frequency sensitivity can then be calculated as 2.36?μN/Hz using the developed model. The coupled domain analysis fits well with the experimental data. Further reduction of quartz thickness and optimization of the thickness ratio of the magnetostrictive to quartz layers offers the possibility of exploiting the stress sensitivity of plate microresonators as sensitive magnetic field sensors capable of low nanoTesla to picoTesla level magnetic flux densities. [ABSTRACT FROM AUTHOR]

In this study, sheet mica was explored as an alternative substrate for thin film deposition due to its unique layered structure and atomically flat surface. Static magnetic properties and microwave permeability of sputtered FeCoN films on mica with and without SiO2 under-layer were examined. In-plane isotropy and a large coercivity of 70 Oe were observed for the film directly deposited on mica substrate. With the insertion of 40 nm SiO2 under-layer between the film and mica substrate, well-defined in-plane anisotropy is formed due to the significant reduce in film residual stress, associated with a 3 Oe coercive force along easy axis. As a result, excellent microwave properties have been achieved and are comparable with the same film on Si substrate. Moreover, the permeability spectra are surprisingly stable from room temperature up to 390 K. Mica is proved as a promising substrate for magnetic films with high microwave performance, which is a great advantage for practical applications. Furthermore, our results provide an effective way to reduce the residual stress in sputtered films. [ABSTRACT FROM AUTHOR]

A device for the imaging of magnetic fields and domain structures based on the Faraday effect has been developed using garnet thin films prepared by the metal-organic decomposition method as indicators. The sensitivity was improved by using high concentration bismuth substituted yttrium iron garnet thin films with in-plane magnetic anisotropy. Low temperature synthesis of the films (BixY3-xFe5O12; x=2) on glass substrates of thickness about 0.8 μm is described and the Faraday rotation angle is measured to be about -11°/μm. [ABSTRACT FROM AUTHOR]

We describe a correlation between electrical resistivity and grain size for PVD synthesized polycrystalline oxide-hardened metal-matrix thin films in oxide-dilute (<5 vol.% oxide phase) compositions. The correlation is based on the Mayadas-Shatzkes (M-S) electron scattering model, predictive of grain size evolution as a function of composition in the oxide-dilute regime for 2 lm thick Au-ZnO films. We describe a technique to investigate grain boundary (GB) mobility and the thermal stability of GBs based on in situ electrical resistivity measurements during annealing experiments, interpreted using a combination of the M-S model and the Michels et al. model describing solute drag stabilized grain growth kinetics. Using this technique, activation energy and pre-exponential Arrhenius parameter values of Ea=21.6 kJ/mol and Ao=2.3 × 10-17 m2/s for Au- 1 vol.% ZnO and Ea=12.7 kJ/mol and Ao=3.1 × 10-18 m2/s for Au-2 vol.% ZnO were determined. In the oxide-dilute regime, the grain size reduction of the Au matrix yielded a maximum hardness of 2.6 GPa for 5 vol.% ZnO. A combined model including percolation behavior and grain refinement is presented that accurately describes the composition dependent change in electrical resistivity throughout the entire composition range for Au-ZnO thin films. The proposed correlations are supported by microstructural characterization using transmission electron microscopy and electron diffraction mapping for grain size determination. [ABSTRACT FROM AUTHOR]

Mn3Ga films were grown by rf-sputtering on SiO2/Si(001) substrates at 300 °C. Ultra-thin films with 2 nm of thickness are composed of small grains with an in-plane diameter ~27 nm. The film exhibits an out-of-plane saturation magnetization Ms 690 emu/cm3 (15 times the bulk magnetization value) and in-plane Ms∥=216 emu/cm3, corresponding to 3.3 and 0.4 μB/Mn at. Giant magnetization is attributed to uncompensated Mn moments located at the intergrain boundaries. No surface anisotropy is expected due to the high anisotropy constant of Mn3Ga. Ms decreases as the film thickness increases due to grain growth and subsequent decrease in intergrain boundary surface area. Magnetic M(H) loops remain anhysteretic for thickness ⩽10 nm, corresponding to an average grain size <50 nm, suggesting that nanocrystals are magnetic monodomains. Films with thickness >10 nm exhibit coercivity between 9 and 19 kOe and Ms from 25 to 72 emu/cm3 with a residual weak ferromagnetic component. Hysteretic M(H) loops are the signature of the existence of magnetic multidomain grains with average grain size >50 nm. All films exhibit higher out-of-plane Ms than in-plane magnetization. [ABSTRACT FROM AUTHOR]

SrRuO3 (SRO) thin films with different thickness (2-70 nm) have been grown on (001), (110), and (111) SrTiO3 substrates. The (001)-SRO films (2-8 nm) exhibited smooth flat surfaces whereas the (110)- and (111)-SRO films featured a faceted island structure. Room temperature resistivity and residual resistivity are the lowest for the (111)-SRO films (30-70 nm). Over all thicknesses, we observed enhanced magnetization in the (111)-SRO films (~4μB/Ru) compared with that for the (001)- and (110)-SRO films (~2μB/Ru and ~3μB/Ru, respectively), suggesting a low-spin state t2g(3↑,1↓), high-spin state t2g(3↑)eg(1↑), and mixed low- and high-spin states for the (001)-, (111)-, and (110)-SRO films, respectively. The dependence of resistivity on temperatures near TC follows a power law with exponent β=0.312 and β=0.363 for the (110)- and (111)-SRO films, respectively. These critical exponents are consistent with magnetic data with scaling law M=C (TC - T)β. At low temperatures, dM/dT and dq/dT show a linear relationship in the temperature range for the Fermi liquid. These results suggest that the intrinsic electrical and magnetic transport properties are coupled. [ABSTRACT FROM AUTHOR]

In this work, the microwave magnetic properties of oblique deposited CoHf/Ta multilayers were investigated. The high frequency magnetic properties of CoHf/Ta multilayers showed different behaviors with oblique angle for different Ta interlayer thickness t. For example, when the Ta interlayer thickness fixed as 5.0 nm, the resonance frequency fr increased from 2.1 to 3.4 GHz with the oblique deposition angle ϑ changing from 10° to 30°. However, when the Ta layer fixed as 15.0 nm, the fr decreased from 2.5 to 1.7 GHz with the oblique deposition angle changing in the same range. The opposite behavior of the fr with ϑ is supposed to result from the existence of the Ta buffer layer, in which the thicker Ta interlayer may hinder the self-shadow effects of the CoHf magnetic layers. [ABSTRACT FROM AUTHOR]

Highly cation-ordered (100) and (110)-oriented PbSc0.5Ta0.5O3 (PST) films were deposited on buffered Si (100) substrates using pulsed laser deposition. Switching of crystal orientation from (100) to (110) was achieved by replacing the Si (100)/ZrO2:Y2O3 (100)/CeO2 (100)/LaNiO3 (100)/PST (100) heterostructure with Si (100)/ZrO2:Y2O3 (YSZ) (100)/SrRuO3 (110)/PST (110). The out-of-plane and in-plane crystal orientation and internal microstructure of (001) and (110) PST films were analyzed in detail by X-ray diffraction, pole figure measurements, and transmission electron microscopy. XRD superstructure reflections indicate that both (100) and (110) PST films are highly cation-ordered and transmission electron microscopy measurements show nano-domains of 15 nm size. The electrical measurements show that the PST films are ferroelectric and that the ferroelectric properties are linked to the microstructure. We have demonstrated the successful integration of PST films on Si substrates with control on growth orientation; this approach can be extended to other oxides to be integrated on silicon substrates for future device applications. [ABSTRACT FROM AUTHOR]

Magnetoelectric bilayered Pb(Zr0.52Ti0.48)O3-CoFe2O4(PZT-CFO) films with different PZT thicknesses were grown on (111)Pt/Ti/SiO2/Si substrates using chemical solution spin-coating. Structural characterization by X-ray diffraction and electron microscopy shows pure phases and well-defined interfaces between the PZT and CFO films. The CFO-PZT-substrate structure effectively alleviates the substrate clamping effect for the CFO layer, showing appreciable magnetoelectric responses in the composite films. Both the direct magnetoelectric effect and the magnetic field-induced Raman shifts in the A1(TO1) soft mode of PZT demonstrate the magnetic- mechanical-electric coupling in the films. The results also indicate that with a constant CFO layer thickness, the thickness of the PZT layer plays an important role in the stress relaxation and strong magnetoelectric coupling. The coupling could be further enhanced by increasing the CFO thickness, optimizing the volume (thickness) fraction of the PZT thickness, and releasing the clamping effect from the substrate. [ABSTRACT FROM AUTHOR]

We have studied structural and magnetic properties of Ta∣CoFeB∣MgO heterostructures using cross-section transmission electron microscopy (TEM), electron energy loss spectrum (EELS) imaging, and vibrating sample magnetometry. From the TEM studies, the CoFeB layer is found to be predominantly amorphous for as deposited films, whereas small crystallites, diameter of ∼5nm, are observed in films annealed at 300 °C. We find that the presence of such nanocrystallites is not sufficient for the occurrence of perpendicular magnetic anisotropy. Using EELS, we find that boron diffuses into the Ta underlayer upon annealing. The Ta underlayer thickness dependence of the magnetic anisotropy indicates that ∼0.2 nm of Ta underlayer is enough to absorb the boron from the CoFeB layer and induce perpendicular magnetic anisotropy. Boron diffusion upon annealing becomes limited when the CoFeB layer thickness is larger than ∼2 nm, which coincides with the thickness at which the saturation magnetization MS and the interface magnetic anisotropy KI drop by ∼20%. These results show the direct role which boron plays in determining the perpendicular magnetic anisotropy in CoFeB∣MgO heterostructures. [ABSTRACT FROM AUTHOR]

The microscopic magnetic properties of high-quality GdN thin films have been investigated by electron spin resonance (ESR) and ferromagnetic resonance (FMR) measurements. Detailed temperature dependence ESR measurements have shown the existence of two ferromagnetic components at lower temperatures, which was not clear from the previous magnetization measurements. The temperature, where the resonance shift occurs for the major ferromagnetic component, seems to be consistent with the Curie temperature obtained from the previous magnetization measurement. On the other hand, the divergence of line width is observed around 57K for the minor ferromagnetic component. The magnetic anisotropies of GdN thin films have been obtained by the analysis of FMR angular dependence observed at 4.2K. Combining the X-ray diffraction results, the correlation between the magnetic anisotropies and the lattice constants is discussed. [ABSTRACT FROM AUTHOR]

Ni-Mn-Ga ferromagnetic shape memory films with similar thickness and chemical composition, deposited onto cold (with a subsequent annealing) and hot MgO(001) substrates exhibit different internal stress and structure giving rise to a different orientation of the magnetic easy axes. A quantitative theoretical analysis of the crystallographic and ferromagnetic resonance (FMR) data shows that the different anisotropies can be caused by the difference in sign between the transformation volume changes in these films, as influenced by the internal stresses. To explain FMR data, the magnetoelastic coupling term of fourth-order in the magnetic vector and linear in the strain tensor components, appearing in the Landau expansion for the free energy, is taken into account. The coefficient of the term, which couples the magnetic vector components with the volume change of the Ni-Mn-Ga alloy, was estimated to be equal to about 107 erg cm-3. [ABSTRACT FROM AUTHOR]

Single and double layer phase change memory structures based on GeTe and GaSb thin films were deposited by pulsed laser deposition (PLD). Their crystallization behavior was studied using in-situ synchrotron techniques. Electrical resistance vs. temperature investigations, using the four points probe method, showed transition temperatures of 138 °C and 198 °C for GeTe and GaSb single films, respectively. It was found that after GeTe crystallization in the stacked films, Ga atoms from the GaSb layer diffused in the vacancies of the GeTe crystalline structure. Therefore, the crystallization temperature of the Sb-rich GaSb layer is decreased by more than 30 °C. Furthermore, at 210 °C, the antimony excess from GaSb films crystallizes as a secondary phase. At higher annealing temperatures, the crystalline Sb phase increased on the expense of GaSb crystalline phase which was reduced. Extended X-ray absorption fine structure (EXAFS) measurements at the Ga and Ge K-edges revealed changes in their local atomic environments as a function of the annealing temperature. Simulations unveil a tetrahedral configuration in the amorphous state and octahedral configuration in the crystalline state for Ge atoms, while Ga is four-fold coordinated in both as-deposited and annealed samples. [ABSTRACT FROM AUTHOR]

Two-phase multiferroic heterostructures composed of room-temperature ferroelectric BaTiO3 (BTO) and ferromagnetic La0.7Sr0.3MnO3 (LSMO) epitaxial thin films were grown on technologically important substrate Si (100). Bilayers of BTO/LSMO thin films display ferromagnetic Curie transition temperatures of ~350K, close to the bulk value, which are independent of BTO films thickness in the range of 25–100 nm. Discontinuous magnetization jumps associated with BTO structural transitions were suppressed in M(T) curves, probably due to substrate clamping effect. Interestingly, at cryogenic temperatures, the BTO/LSMO structure with BTO layer thickness of 100 nm shows almost 2-fold higher magnetic coercive field, 3-fold reduction in saturation magnetization, and improved squareness compared to the sample without BTO. We believe that the strong in-plane spin pinning of the ferromagnetic layer induced by BTO layer at BTO/LSMO interface could cause such changes in magnetic properties. This work forms a significant step forward in the integration of two-phase multiferroic heterostructures for CMOS applications. [ABSTRACT FROM AUTHOR]

We report on a systematical study of the structure, magnetism, and magnetotransport behavior of the hexagonal MnNiGa films deposited on thermally oxidized Si (001) substrates by magnetron sputtering. X-ray diffractions reveal that all the films deposited at different temperatures crystallized in hexagonal Ni2In-type structure (space group P63/mmc). Scanning electron microscopy observations show that the surface morphology of the films varies with deposition temperature, and energy dispersive spectroscopy analysis shows compositions of the films remain nearly unchanged, independent of the deposition temperature. Magnetic measurements indicate that all films are ferromagnetic and exhibit a magnetic anisotropy behavior. The magnetoresistance (MR) exhibits a negative temperature- and field-dependent behavior. The possible origin of the negative MR is discussed. Furthermore, we found that the Hall effect is dominated by an anomalous Hall effect (AHE) only due to skew scattering independent of the deposition temperature of films. Moreover, the anomalous Hall resistivity presents a non-monotonously temperature-dependent behavior. [ABSTRACT FROM AUTHOR]

The effect of atomic layer deposition (ALD) growth temperature on the interfacial characteristics of p-GaAs MOS capacitors with ALD HfO2 high-k dielectric using tetrakis(ethylmethyl)amino halfnium precursor is investigated in this study. Using the combination of capacitance-voltage (C-V) and X-ray photoelectron spectroscopy (XPS) measurements, ALD growth temperature is found to play a large role in controlling the reaction between interfacial oxides and precursor and ultimately determining the interface properties. The reduction of surface oxides is observed to be insignificant for ALD at 200 °C, while markedly pronounced for growth at 300 °C. The corresponding C-V characteristics are also shown to be ALD temperature dependent and match well with the XPS results. Thus, proper ALD process is crucial in optimizing the interface quality. [ABSTRACT FROM AUTHOR]

In structurally ordered magnetic thin films, the Curie temperature (TC) of ferromagnetic films depends on the exchange integral of the short range ordered neighboring atoms. The exchange integral may be adjusted by controlling the elemental substitutional concentration at the lattice site of interest. We show how to control the TC in high anisotropy L10 Fe50 Pt50 magnetic thin films by substituting Rh into the Pt site. Rh substitution in L10 FePt modified the local atomic environment and the corresponding electronic properties, while retaining the ordered L10 phase. The analysis of extended x-ray Absorption Fine Structure spectra shows that Rh uniformly substitutes for Pt in L10 FePt. A model of antiferromagnetic defects caused by controlled Rh substitution of the Pt site, reducing the TC, is proposed to interpret this phenomenon and its validity is further examined by ab initio density functional calculations. [ABSTRACT FROM AUTHOR]

The emergence of ferromagnetism in materials where the bulk phase does not show any magnetic order demonstrates that atomically precise films can stabilize distinct ground states and expands the phase space for the discovery of materials. Here, the emergence of long-range magnetic order is reported in ultrathin (111) LaNiO3 (LNO) films, where bulk LNO is paramagnetic, and the origins of this phase are explained. Transport and structural studies of LNO(111) films indicate that NiO6 octahedral distortions stabilize a magnetic insulating phase at the film/substrate interface and result in a thickness-dependent metal–insulator transition at t = 8 unit cells. Away from this interface, distortions relax and bulk-like conduction is regained. Synchrotron x-ray diffraction and dynamical x-ray diffraction simulations confirm a corresponding out-of-plane unit-cell expansion at the interface of all films. X-ray absorption spectroscopy reveals that distortion stabilizes an increased concentration of Ni2+ ions. Evidence of long-range magnetic order is found in anomalous Hall effect and magnetoresistance measurements, likely due to ferromagnetic superexchange interactions among Ni2+–Ni3+ ions. Together, these results indicate that long-range magnetic ordering and metallicity in LNO(111) films emerges from a balance among the spin, charge, lattice, and orbital degrees of freedom. [ABSTRACT FROM AUTHOR]

In this study, [Co/Ni]2/PtMn thin films with different PtMn thicknesses (2.7 to 32.4 nm) were prepared on Si/SiO2 substrates. The post-deposition perpendicular magnetic field annealing (MFA) processes were carried out to modify the structures and magnetic properties. The MFA process also induced strong interlayer diffusion, rendering a less sharp interface between Co and Ni and PtMn layers. The transmission electron microscopy (TEM) lattice image analysis has shown that the films consisted of face-centered tetragonal (fct) PtMn (ordered by MFA), body-centered cubic (bcc) NiMn (due to intermixing), in addition to face-centered cubic (fcc) Co, Ni, and PtMn phases. The peak shift (2-theta from 39.9°C to 40.3°C) in X-ray diffraction spectra also confirmed the structural transition from fcc PtMn to fct PtMn after MFA, in agreement with those obtained by lattice images in TEM. The interdiffusion induced by MFA was also evidenced by the depth profile of X-ray photoelectron spectroscopy (XPS). Further, the magnetic properties measured by vibrating sample magnetometry (VSM) have shown an increased coercivity in MFA-treated samples. This is attributed to the presence of ordered fct PtMn, and NiMn phases exchange coupled to the ferromagnetic [Co/Ni]2 layers. The vertical shift (Mshift = -0.03 memu) of the hysteresis loops is ascribed to the pinned spins resulting from perpendicular MFA processes. [ABSTRACT FROM AUTHOR]

We have fabricated a high quality magnetic Ni0.5Zn0.5Fe2O4 ferrite powder/polymer composite sheet consisting of common and environmentally friendly elements only. The sheet was then tested for its dynamic permeability by irradiating with electromagnetic waves with frequencies up to 50 GHz. Two different originally developed methods were used for the high-frequency permeability measurements, a short-circuited microstrip line method and a microstrip line-probe method. It is challenging to measure the dynamic permeability of magnetic thin films/sheets beyond 10 GHz because of the low response signal from these materials. However, the two methods produced essentially equivalent results. In the frequency dependent permeability profile, the maximum position of the profile, μ max ″ , shifted towards higher frequencies upon increasing an applied (strong) static external magnetic field, H dc . A linear relationship between μ max ″ and H dc for the entire range of H dc was observed even at small H dc . In general, the spinel-structured Ni-based ferrites exhibit low magnetic anisotropy, but the present sample showed a uniaxial-anisotropic behavior in the parallel direction of the sheet. Our Ni0.5Zn0.5Fe2O4 powder/polymer composite sheet thus exhibits high performance at GHz frequencies, and should be applicable e.g. as an anisotropic electromagnetic wave-interference material. [ABSTRACT FROM AUTHOR]

In this paper, we report on the epitaxial integration of room temperature lead-free ferroelectric BaTiO3 thin (~1050 nm) films on Si (100) substrates by pulsed laser deposition technique through a domain matching epitaxy paradigm. We employed MgO and TiN as buffer layers to create BaTiO3/SrRuO3/MgO/TiN/Si (100) heterostructures. C-axis oriented and cube-on-cube epitaxial BaTiO3 is formed on Si (100) as evidenced by the in-plane and out-of-plane x-ray diffraction, and transmission electron microscopy. X-ray photoemission spectroscopic measurements show that Ti is in 4(+) state. Polarization hysteresis measurements together with Raman spectroscopy and temperature-dependent x-ray diffraction confirm the room temperature ferroelectric nature of BaTiO3. Furthermore, laser irradiation of BaTiO3 thin film is found to induce ferromagnetic-like behavior but affects adversely the ferroelectric characteristics. Laser irradiation induced ferromagnetic properties seem to originate from the creation of oxygen vacancies, whereas the pristine BaTiO3 shows diamagnetic behavior, as expected. This work has opened up the route for the integration of room temperature lead-free ferroelectric functional oxides on a silicon platform. [ABSTRACT FROM AUTHOR]

In this work, we deposited FeCoN thin films by reactive dc magnetron sputtering under various deposition powers. Composition, microstructure, static magnetic properties, and microwave permeability of as-sputtered films were examined. The permeability spectra were theoretically analyzed based on LLG equation. When high deposition power was applied, μ0' improved significantly due to the increased Mi and decreased Hk. On the other hand, the damping coefficient λ increased with the power, which resulted in the widen permeability spectra. The physical origin of the influences should be related to the change in the film composition and microstructure, which have immediate impact on static magnetic properties and damping effect of the film. [ABSTRACT FROM AUTHOR]

The magneto-optic surface plasmon resonance in transverse geometry of glass/Au/IrMn/Co/Au/dielectric exchange biased thin film systems has been studied as a function of the Au-cap layer thickness for the dielectric air and water. The results show that it is possible to achieve either an optimum steepness of the reflectivity as compared to a glass/Au/dielectric layer system or to maximize the magneto-optic activity. As the Au-cap layer thickness is increased, the magneto-optic activity is reduced whereas the steepness of the reflectivity in the range of the resonance is raised. The width of the reflectivity curves and the magneto-optic signals is broadened for thin Au-capping layers. [ABSTRACT FROM AUTHOR]

Intrinsically tunable bulk acoustic wave resonators, based on sol-gel 0.70Pb(Mg1/3Nb2/3)O3- 0.30PbTiO3 (PMN-PT) thin films, with high effective electromechanical coupling coefficient of 13% and tunability of the series resonance frequency up to 4.0% are fabricated and characterized. The enhanced electroacoustic properties of the PMN-PT resonators are attributed to the mechanism of polarization rotation occurring in the region of the morphotropic phase boundary. Electroacoustic performance of the PMN-PT resonators is analyzed using the theory of dc fieldinduced piezoelectric effect in ferroelectrics. Extrinsic acoustic loss in the PMN-PT resonators is analyzed using the model of the wave scattering at reflections from rough interfaces. Mechanical Q-factor of the resonators is up to 70 at 4.1 GHz and limited mainly by losses in the PMN-PT film. [ABSTRACT FROM AUTHOR]

We study the effect of one-side metallization of a uniform ferromagnetic thin film on its spin-wave dispersion relation in the Damon-Eshbach geometry. Due to the finite conductivity of the metallic cover layer on the ferromagnetic film, the spin-wave dispersion relation may be nonreciprocal only in a limited wave-vector range. We provide an approximate analytical solution for the spin-wave frequency, discuss its validity, and compare it with numerical results. The dispersion is analyzed systematically by varying the parameters of the ferromagnetic film, the metal cover layer and the value of the external magnetic field. The conclusions drawn from this analysis allow us to define a structure based on a 30 nm thick CoFeB film with an experimentally accessible nonreciprocal dispersion relation in a relatively wide wave-vector range. [ABSTRACT FROM AUTHOR]

X-ray photoelectron spectroscopy was performed on Mn2-xCo2xNi1-xO4 (x=0.2, 0.4, 0.5, 0.6, and 0.8) series spinel films to determine their cation distributions. The results show that both Ni and Co ions exhibit bivalence, while Mn ions exhibit coexisting multivalence. The hopping frequency v0 of each sample was obtained by combining cation distribution results and electrical measurement data. Analysis of the divergence at Neel temperature between field cooling and zero-field cooling magnetization curves revealed that the ferromagnetic coupling between octahedral site ions first leads to spontaneous magnetization at TC, after which a second spontaneous magnetization arises from the antiferromagnetic couple between tetrahedral and octahedral sites at a lower temperature TN. The correlation between hopping conductivity and magnetic transition temperature is discussed. We propose that the strength of the ferromagnetic couple between octahedral sites is subject to the product term of Nc(1-c)v0, which determines the ferromagnetic transition temperature (TC) of the system. Our results provide an avenue to understand the origin of magnetic interaction in small-polaron hopping semiconductors. [ABSTRACT FROM AUTHOR]

Double perovskite Nd2CoMnO6 thin films have been grown epitaxially on SrTiO3 substrates using pulsed laser deposition and their structural, magnetic, and dielectric properties were investigated. Temperature dependent dielectric (ε) constant is measured in the frequency range between 1 kHz and 1 MHz under applied magnetic fields up to 0.5 kOe. The dielectric constant exhibits an anomaly near to the Curie temperature which is independent of magnetic field and can be corroborated with a loop opening temperature in zero-field-cooled and field-cooled magnetization measurements. While, a linear relationship between magnetodielectric constant, δεMD, and M²(magnetization) in the paramagnetic to ferromagnetic regime proves magnetodielectric coupling between ferroelectric and ferromagnetic orders in this single-phase perovskite system. [ABSTRACT FROM AUTHOR]

Oriented Strontium Ferrite films with the c axis orientation were deposited with varying oxygen partial pressure on Al2O3(0001) substrate using Pulsed Laser Deposition technique. The angle dependent magnetic hysteresis, remanent coercivity, and temperature dependent coercivity had been employed to understand the magnetization reversal of these films. It was found that the Strontium Ferrite thin film grown at lower (higher) oxygen partial pressure shows Stoner-Wohlfarth type (Kondorsky like) reversal. The relative importance of pinning and nucleation processes during magnetization reversal is used to explain the type of the magnetization reversal with different oxygen partial pressure during growth. [ABSTRACT FROM AUTHOR]

We report on the modification of the thermoelectric properties of poly(3, 4 ethylenedioxylthiophene): poly(styrenesulfonate) (PEDOT:PSS) thin films by means of a simple post treatment of the solid thin films realized by drop-coating. We show that the organic polar solvents, dimethyl sulfoxide and ethylene glycol as secondary dopants for PEDOT:PSS, only affect the film morphology for which a high electrical conductivity is observed. In contrast, ethanolamine (MEA) and ammonia solutions are reduction agents that improve the density of PEDOT chains in the reduced forms (polaron and neutral states), resulting in the trade-off between Seebeck coefficient and electrical conductivity. Furthermore, we show that the nature of amines determines the reduction degree: the nitrogen lone pair electrons in MEA are easier to be donated than those in ammonia solution and will therefore neutralize the PEDOT chains. [ABSTRACT FROM AUTHOR]

In this work, the hysteresis loops of ultra thin CoFeB films with perpendicular anisotropy are simulated using a micromagnetic model with microstructure included. An inhomogeneous region of the perpendicular uniaxial anisotropy constant K is introduced in the model, and this is the key factor to explain why the in-plane saturation field is several thousand Oersted, while the perpendicular coercivity can be on the order of 100 Oersted. Tendency of the simulated loops with increasing total simulation size reveals that this model is reliable, and the calculated loops basically agree with experiments. The effects of different K distribution, defect sizes, defect patterns, and higher order magnetic anisotropy on simulated M-H loops are also discussed in the paper. [ABSTRACT FROM AUTHOR]

The present work studies the effect of substrate temperature and film composition on the structural and mechanical properties evolution of magnetron sputtered Zr-Ti films. As-deposited films show a monotonically strengthening (0002) crystallographic texture ranging from ambient temperature to 523 K, while then reveal a (0002) texture to randomly orientated structure transition at higher temperature. High Resolution TEM observations reveal a competitive and reconstruction growth mechanism which is in good agreement with the well-known Structure Zone Model. Nano-indentation measurements revealed that texture strengthening contribute to the improvement of mechanical properties. These results suggest that by establishing a semi-quantitative phase diagram based on the Structure Zone Model, structure and structure-related properties modification can be easily realized and precisely controlled by modifying the TS/Tm region during deposition. [ABSTRACT FROM AUTHOR]

Incorporation of magnetic dopants into topological insulators to break time-reversal symmetry is a prerequisite for observing the quantum anomalous Hall (QAHE) effect and other novel magnetoelectric phenomena. GdBiTe3 with a Gd:Bi ratio of 1:1 is a proposed QAHE system, however, the reported solubility limit for Gd doping into Bi2Te3 bulk crystals is between ~0.01 and 0.05. We present a magnetic study of molecular beam epitaxy grown (GdxBi1-x)2Te3 thin films with a high Gd concentration, up to x ≈ 0.3. Magnetometry reveals that the films are paramagnetic down to 1.5 K. X-ray magnetic circular dichroism at the Gd M4,5 edge at 1.5 K reveals a saturation field of ~6T, and a slow decay of the magnetic moment with temperature up to 200 K. The Gd3+ ions, which are substitutional on Bi sites in the Bi2Te3 lattice, exhibit a large atomic moment of ~7 μB, as determined by bulk-sensitive superconducting quantum interference device magnetometry. Surface oxidation and the formation of Gd2O3 lead to a reduced moment of ~4/μB as determined by surface-sensitive x-ray magnetic circular dichroism. Their large atomic moment makes these films suitable for incorporation into heterostructures, where interface polarization effects can lead to the formation of magnetic order within the topological insulators. [ABSTRACT FROM AUTHOR]

Broadband magnetization response of equilateral triangular 1000 nm Permalloy dots has been studied under an in-plane magnetic field, applied parallel (buckle state), and perpendicular (Y state) to the triangles base. Micromagnetic simulations identify edge spin waves (E-SWs) in the buckle state as SWs propagating along the two adjacent edges. These quasi one-dimensional spin waves emitted by the vertex magnetic charges gradually transform from propagating to standing due to interference and are weakly affected by dipolar interdot interaction and variation of the aspect ratio. Spin waves in the Y state have a two dimensional character. These findings open perspectives for implementation of the E-SWs in magnonic crystals and thin films. [ABSTRACT FROM AUTHOR]

We have investigated the origin of thickness dependent spin reorientation transition (SRT) of B2 type FeCo alloy using the full potential linearized augmented plane wave method. It has been reported that FeCo alloy films on various substrates show a SRT from perpendicular to in-plane magnetization at an approximate thickness of 15 monolayers (MLs). The enhanced perpendicular magnetic anisotropy in bulk FeCo is attributed to a tetragonal distortion. However, we have found that the tetragonal distortion tends to suppress the magnetocrystalline anisotropy (MCA) energy at increasing film thickness in two-dimensional structure. In contrast, the magnitude of the shape anisotropy energy increases at increasing FeCo film thickness. Interestingly, the shape anisotropy overcomes the MCA and the SRT, from perpendicular anisotropy to in-plane magnetization, which occurs at a thickness of 15 ML. Consequently, we are able to clearly understand the physical mechanism of the thickness dependent SRT in terms of the competing reactions of these two counteracting contributions. [ABSTRACT FROM AUTHOR]

Static and dynamic magnetic properties of composition-graded FeCoTa thin films were systematically studied with respect to temperature and the deposition power of Ta target. The magnetic anisotropy field and ferromagnetic resonance frequency were found to be increased with the increasing of deposition power of Ta target due to the enhancement of stress when Ta concentration is increased. Thermal stability of the films shows a very interesting behavior with a peculiar and large increasing of magnetic anisotropy with temperature when the deposition power for Ta is moderate while it exhibits normal decreasing with temperature when the deposition power is low or high. The results are discussed and explained in terms of the magneto-elastic anisotropy contribution when the stress of the films is varied. [ABSTRACT FROM AUTHOR]

Chemically ordered and highly textured L10 FePt-C granular films are potential media for future heat-assisted magnetic recording. Vibrating sample magnetometry of such films in fields up to 14 T reveals a perpendicular coercivity of up to μ0HC=4.92 T and an anisotropy field of μ0HA=9.2 T, which translates to a (uni-axial) anisotropy constant as high as KU=5.3 MJ/m3. An analysis of the remanent magnetization and demagnetization curves shows that the spatially separated FePt nanoparticles act as a Stoner-Wohlfarth ensemble of uni-axial nanomagnets with negligible dipolar inter-particle coupling. The magnetic texture spread of 23° as determined from an analysis of the hard axis magnetization curve is found to be clearly larger than the structural texture width of roughly 3°. Aberration corrected high-resolution transmission electron microscopy reveals that the latter is due to the remaining roughness of the seed layer that causes the particle growth to nucleate at step edges of this layer. [ABSTRACT FROM AUTHOR]

We have fabricated a cross-bar Hall sensor made of 50-nm-wide and 100-nm-thick bismuth wires patterned by an electron-beam lithography and lift-off. The Hall coefficient at 300 K is as large as -0.44 cm3/C, yielding in a high product sensitivity of about 5 V/(A T). The series resistance was reduced as low as 1.7 kΩ with a short bar configuration, resulting in a high signal-to-noise ratio of 38.5 dB. These characteristics are far better than those reported with similar dimensions. The Hall element was successfully demonstrated for detecting the domain wall motion in an iron garnet film employed as the substrate. [ABSTRACT FROM AUTHOR]

Highly crystalline corundum structured α-(Ga0.42Fe0.58)2O3 alloy thin film showed magnetic properties at room temperature. Microstructure analysis of cross-sectional transmission electron microscope (TEM) observation and TEM energy dispersive X-ray spectroscopy measurement indicated that different crystal phase could not be detected as well as there is no remarkable phase separating area, that is, Fe and Ga ions are distributed uniformly in the film. Magnetic measurements were performed on α-(Ga1-xFex)2O3 (x = 0.24, 0.44, 0.58, 1.00) alloy thin films at 110 K. The induced magnetic moment per a Fe ion of α-(Ga0.42Fe0.58)2O3 at 5000 Oe is about 6 times larger than α-Fe2O3 thin film. Compared to the α-Fe2O3 thin films, the value of coercivity is also about 6 times in α-(Ga0.42Fe0.58)2O3, in contrast, there is no significant difference in value of coercivity of α-(Ga1-xFex)2O3 (x = 0.24, 0.44, 1.00) thin films. These means that the origin of magnetism is not the separation region of α-Fe2O3 in α-(Ga0.42Fe0.58)2O3 thin film. [ABSTRACT FROM AUTHOR]

We provide experimental evidence for a vortex migration phenomenon in YBa2Cu3O7-δ (YBCO) thin film caused by travelling magnetic wave. The experiment is carried out on a 2 in. diameter YBCO thin film with a circular-type magnetic flux pump. We found that the travelling wave helps the vortices migrate into the centre of the sample: after the zero-field cooling process, the increase of the flux density in the centre is four times larger than the amplitude of the travelling wave. The reason for this massive vortex migration is probably due to the magnetic stress variation caused by the travelling wave: the magnetic stress increases locally in the crest region while decreases locally in the trough region, which could help the vortices to move locally. A comparison shows that the magnetization by standing wave can be easily predicted by Bean's model while travelling wave causes vortex migration generally much larger than the prediction of Bean's model. It is possible that travelling magnetic wave can be an effective way to magnetize a type II superconductor in considering this unusual vortex dynamics. [ABSTRACT FROM AUTHOR]

The temperature scaling of the ferroelectric hysteresis was first investigated in (K,Na)NbO3 films grown on SrRuO3/SrTiO3 over a temperature range from 100 K to 340 K. The power-law temperature scaling relations were obtained for , Pr, and Ec in the two distinguished temperature regions, separated by T ∼ 245 K. It was observed that and Pr had a similar temperature dependence, compared with Ec. With increasing T, and Pr decreased in the first region, and increased in the second region. While Ec decreased in the whole temperature range, but with different decrease rate in the two temperature regions. [ABSTRACT FROM AUTHOR]

Hydrogenated microcrystalline silicon (μc-Si:H) thin films were prepared by remote low frequency inductively coupled plasma (ICP) chemical vapor deposition system, and the effect of silane/hydrogen ratio on the microstructure and electrical properties of μc-Si:H films was systematically investigated. As silane/hydrogen ratio increases, the crystalline volume fraction Fc decreases and the ratio of the intensity of (220) peak to that of (111) peak drops as silane flow rate is increased. The FTIR result indicates that the μc-Si:H films prepared by remote ICP have a high optical response with a low hydrogen content, which is in favor of reducing light-induced degradation effect. Furthermore, the processing window of the phase transition region for remote ICP is much wider than that for typical ICP. The photosensitivity of μc-Si:H films can exceed 100 at the transition region and this ensures the possibility of the fabrication of microcrystalline silicon thin film solar cells with a open-circuit voltage of about 700 mV. [ABSTRACT FROM AUTHOR]