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In ${\mathrm{Ta/(Co,Fe)B/HfO}}_{2}$ stacks, a gate voltage drives, in a nonvolatile way, the system from an underoxidized state exhibiting in-plane anisotropy (IPA) to an optimum oxidation level resulting in perpendicular anisotropy (PMA) and further into an overoxidized state with IPA. The $\mathrm{IPA}\phantom{\rule{0.1em}{0ex}}\ensuremath{\rightarrow}\phantom{\rule{0.1em}{0ex}}\mathrm{PMA}$ regime is found to be significantly faster than the $\mathrm{PMA}\phantom{\rule{0.1em}{0ex}}\ensuremath{\rightarrow}\phantom{\rule{0.1em}{0ex}}\mathrm{IPA}$ regime, whereas only the latter shows full reversibility under the same gate voltages. The effective damping parameter also shows a marked dependence with gate voltage in the $\mathrm{IPA}\phantom{\rule{0.1em}{0ex}}\ensuremath{\rightarrow}\phantom{\rule{0.1em}{0ex}}\mathrm{PMA}$ regime, going from 0.029 to 0.012, and only a modest increase to 0.014 in the $\mathrm{PMA}\phantom{\rule{0.1em}{0ex}}\ensuremath{\rightarrow}\phantom{\rule{0.1em}{0ex}}\mathrm{IPA}$ regime. The existence of two magnetoionic regimes has been linked to a difference in the chemical environment of the anchoring points of oxygen species added to underoxidized or overoxidized layers. Our results show that multiple magnetoionic regimes can exist in a single device and that their characterization is of great importance for the design of high-performance spintronics devices.

Ab initio calculations of voltage-controlled perpendicular magnetic anisotropy predict that the adjunction of Pt at the top of Co/MgO interface in Pt/Co/MgO ultrathin structures would enhance the perpendicular anisotropy and its electric field ( $E$ -field) variation rate. Following these theoretical expectations, using the magnetron-sputtering technique, we first designed and elaborated magnetic multilayered samples which have subsequently been patterned by UV lithography in magnetotransport devices. The as-deposited samples show perpendicular magnetization configuration whose $E$ -field modulation has been studied by anomalous Hall effect magnetometry experiments under applied $E$ -field in patterned devices. The measured voltage anisotropy modulation effect is found to be asymmetric with respect to the $E$ -field polarity, in qualitative agreement with theoretical predictions.

Microstrip line ferromagnetic resonance (MS-FMR) and Brillouin light scattering (BLS) in the Damon-Eshbach geometry were used to investigate the perpendicular magnetic anisotropy (PMA), the damping and the interfacial Dzyaloshinskii-Moriya (iDMI) interaction in ferromagnetic $(\mathrm{FM})/\mathrm{Ta}{\mathrm{O}}_{x}\text{\ensuremath{-}}\mathrm{based}$ systems as a function of the ferromagnetic ($\mathrm{FM}=\mathrm{Co}$ or ${\mathrm{Co}}_{8}{\mathrm{Fe}}_{72}{\mathrm{B}}_{20}$) and the $\mathrm{Ta}{\mathrm{O}}_{x}$ thicknesses (oxidation level). The analysis of the experimental FMR and BLS data has shown that the effective magnetization, the Gilbert damping parameter \ensuremath{\alpha} and the iDMI are inversely proportional to the CoFeB and the Co films thickness. The BLS investigation of the iDMI variation versus the $\mathrm{Ta}{\mathrm{O}}_{x}$ thickness and oxidation level reveals a contribution of $\mathrm{FM}/\mathrm{Ta}{\mathrm{O}}_{x}$ mediated by the presence of a Rashba field at this interface. Finally, we evidenced a correlation between iDMI and PMA by varying the Cu spacer thickness in the $\mathrm{Pt}/\mathrm{Cu}/\mathrm{Co}/\mathrm{Ta}{\mathrm{O}}_{x}$ system and we showed that both PMA and iDMI are localized at the first atomic monolayers of the Pt/Co interface. The observed non-linear dependence of PMA versus iDMI constant is attributed to similar interface orbital hybridizations involved in both quantities.

Epitaxial magnetic heterostructures of $\mathrm{Mg}\mathrm{O}(001)//\mathrm{Pd}/{\mathrm{Co}}_{2}\mathrm{Fe}\mathrm{Al}/\mathrm{Mg}\mathrm{O}$ are grown by magnetron sputtering and the current-induced spin-orbit torques are quantified using harmonic Hall measurements. We demonstrate efficient current-induced spin-orbit-torque switching in perpendicularly magnetized samples. The advantage of such heterostructures for spin-orbit-torque magnetic random-access memory devices is that they allow a combination of critical ingredients: (i) the low resistivity required for reduced electric energy consumption during writing, (ii) the compatibility with a high tunnel magnetoresistive ratio required for efficient reading, and (iii) strong perpendicular magnetic anisotropy for increased thermal stability.

Co20Fe60B20 thin films of various thicknesses (3 nm $\le t_{\text {CFB}} \le 14$ nm) have been sputtered on thermally oxidized Si substrates and capped with 8 nm-thick Ir or Ru layers and then annealed at 400 °C. A vibrating sample magnetometer has been used to measure the CoFeB thickness dependence of the saturation magnetic moment per unit area in order to straightforwardly determine the magnetization at saturation and the magnetic dead layer thickness, found to be 1115 ± 50 emu/cm3 (930 ± 50 emu/cm3) and 1.53 nm (0.76 nm) for the as-deposited CoFeB/Ir (CoFeB/Ru) sytems, respectively. These values change to 1185 ± 50 emu/cm3 (1110±50 emu/cm3) and 2.93 nm (1.62 nm) for CoFeB/Ir (CoFeB/Ru) films annealed at 400 °C. Microstrip ferromagnetic resonance (MS-FMR) was used to investigate the Gilbert damping parameter and the magnetic anisotropy as a function of the CoFeB thickness. While the in-plane anisotropy field for the as-deposited films does not show a regular behavior versus the CoFeB thickness, a clear linear behavior of this field versus the reciprocal CoFeB effective thickness can be observed for the annealed samples. Moreover, the effective magnetization varies linearly with the inverse effective thickness of CoFeB due to the perpendicular interface anisotropy. This surface anisotropy constant, which was estimated to be 0.84 and 0.89 erg/cm2 for the as-deposited CoFeB films capped with Ir or Ru, respectively, reinforces the perpendicular easy axis. The corresponding anisotropy constants for the annealed Ir and Ru capped films are found to be 1.07 and 0.57 erg/cm2, respectively. Moreover, MS-FMR results revealed that the damping constant increases linearly with the reciprocal effective thickness of CoFeB, most probably due to spin pumping. The effective spin mixing conductance of the as-deposited (annealed) CoFeB/Ru and CoFeB/Ir has been estimated to be 12.93 nm−2 (22.4 nm−2) and 29.3 nm−2 (43.85 nm−2), respectively.

Brillouin light scattering (BLS) combined with vibrating sample magnetometry (VSM) have been used to investigate the Dzyaloshinskii–Moriya interaction (DMI) in Pt-buffered Co2FeAl0.5Si0.5 ultrathin films of various thicknesses. VSM measurements of the Co2FeAl0.5Si0.5 (CFAS) thickness dependence of the saturation magnetic moment per unit area revealed a magnetization at saturation of 1286 emu/cm3 and 0.31 nm magnetic dead layer. Furthermore, thickest films ( $t_{{\text {CFAS}}} >1$ nm) are in-plane magnetized, while the thinner ones are perpendicular magnetized. BLS measurements, in the Damon–Eshbach geometry, under an in-plane applied magnetic field revealed the non-reciprocity of the spin waves (SWs) propagating in opposite directions (Stokes and anti-Stokes lines) due to the Pt-induced DMI. Stokes and anti-Stokes lines’ frequency mismatch varies linearly as function of the SW vector allowing the determination of the effective DMI constant. Its thickness dependence leads to determine a value of −0.42 pJ/m for the DMI interface constant, which is significantly lower than that of Pt/Co/AlO x films. Moreover, BLS measurements revealed that the effective magnetization varies linearly with the reciprocal effective CFAS thickness due to the perpendicular interface anisotropy, estimated to be 0.49 mJ/m2, which reinforces the perpendicular magnetization easy axis.

This paper describes the synthesis and characterization of YBa2Cu3O7−x (YBCO) nanoparticles obtained through an environmentally friendly chemistry approach. Y-, Cu- acetates and Ba trifluoroacetate were used for the synthesis of the precursor gel. Moreover, sucrose and pectin reagents were added as chelating agents inducing the formation of small size oxide nanoparticles. The thermal decomposition process of the precursor powder was investigated by thermal analysis correlated with mass spectrometry. The chemical nature, structure and morphology of the particles were investigated by X-Ray diffraction (XRD), Transmission Electron Microscopy (TEM) and Fourier Transform Infrared Spectroscopy. According to XRD analysis the nanoparticles have an orthorhombic structure and the average diameter between 18–30 nm, additionally confirmed by TEM measurements. The superparamagnetic behavior at room temperature of the YBCO nanoparticles has been clearly evidenced by magnetization measurements. Furthermore, the effect of the annealing atmosphere on the magnetic properties has been studied.

This paper presents a comparative study regarding the preparation of Fe-based amorphous alloys via mechanical alloying (MA) and rapid quenching (RQ). The obtained samples (powders and ribbons) were characterised by X-ray diffraction (XRD), in-situ high-temperature X-ray diffraction (HT-XRD), differential scanning calorimetry (DSC), thermogravimetry (TG) and vibrating sample magnetometry (VSM). By using elemental powders of Fe, Si and B, it was found that amorphisation cannot be achieved by dry MA or RQ. Wet MA using benzene as process control agent (PCA) led to the alloy amorphisation after 20 h of milling. It was proved that the amorphisation via wet MA is possible due to the extra amount of C atoms provided by the PCA decomposition. Using powders obtained by wet MA or a mixture of Fe, Si, B and C elemental powder, amorphous ribbons were obtained by RQ. During the amorphous samples crystallisation, a mixture of α-Fe(Si) and Fe borides is formed. The magnetic measurements showed that the magnetic characteristics of the samples are strongly influenced by the technique used for their preparation.

Perpendicular magnetic anisotropy (PMA) in ultrathin magnetic structures is a key ingredient for the development of electrically controlled spintronic devices. Due to their relatively large spin-polarization, high Curie temperature and low Gilbert damping the Co-based full Heusler alloys are of special importance from a scientific and applications point of view. Here, we study the mechanisms responsible for the PMA in Pt/Co-based full Heusler alloy/MgO thin films structures. We show that the ultrathin Heusler films exhibit strong PMA even in the absence of magnetic annealing. By means of ferromagnetic resonance experiments, we demonstrate that the effective magnetization shows a two-regime behavior depending on the thickness of the Heusler layers. Using Auger spectroscopy measurements, we evidence interdiffusion at the underlayer/Heusler interface and the formation of an interfacial CoFe-rich layer which causes the two-regime behavior. In the case of the ultrathin films, the interfacial CoFe-rich layer promotes the strong PMA through the electronic hybridization of the metal alloy and oxygen orbitals across the ferromagnet/MgO interface. In addition, the interfacial CoFe-rich layer it is also generating an increase of the Gilbert damping for the ultrathin films beyond the spin-pumping effect. Our results illustrate that the strong PMA is not an intrinsic property of the Heusler/MgO interface but it is actively influenced by the interdiffusion, which can be tuned by a proper choice of the underlayer material, as we show for the case of the Pt, Ta and Cr underlayers., 23 pages, 9 figures

We demonstrate room-temperature stabilization of dipolar magnetic skyrmions with diameters in the range of $100$ nm in a single ultrathin layer of the Heusler alloy Co$_2$FeAl (CFA) under moderate magnetic fields. Current-induced skyrmion dynamics in microwires is studied with a scanning Nitrogen-Vacancy magnetometer operating in the photoluminescence quenching mode. We first demonstrate skyrmion nucleation by spin-orbit torque and show that its efficiency can be significantly improved using tilted magnetic fields, an effect which is not specific to Heusler alloys and could be advantageous for future skyrmion-based devices. We then show that current-induced skyrmion motion remains limited by strong pinning effects, even though CFA is a magnetic material with a low magnetic damping parameter., 5 pages, 4 figures

This study presents the preparation and characterisation of soft magnetic composites (SMCs) in which the powders, that are generally used as the ferromagnetic phase, are replaced by short and thin Fe fibres. The Fe fibres (length of 3–7 mm and thickness of 70–110 μm) were coated with a layer of polymer that represents 1 wt% of the total weight of the fibres. To prepare the toroidal cores, three different mould filling techniques were used with the aim of orienting the fibres with their long axis parallel to the magnetising field. The compaction pressure for the preparation of all compacts was 700 MPa. The fibres used in this study were characterised via scanning electron microscopy (SEM) and vibrating sample magnetometry (VSM). The degree of fibres orientation inside the composite compacts was analysed via energy-dispersive X-ray spectroscopy (EDX). The fibres based composite compacts were analysed in static (DC) and dynamic (AC) magnetisation regime up to the frequency of 10 kHz. The DC and AC magnetisation measurements highlighted that the magnetic characteristics of the compacts increase upon increasing the degree of fibres orientation. A comparison of AC and DC magnetic characteristics of a fibres-based composite and a powder-based composite (prepared in identical conditions) is presented and discussed.

The interfacial Dzyaloshinskii-Moriya interaction (IDMI) is investigated in Co2FeAl (CFA) ultrathin films of various thicknesses (0.8 nm ≤ tCFA ≤ 2nm) grown by sputtering on Si substrates, using Pt, W, Ir, and MgO buffer or/and capping layers. Vibrating sample magnetometry reveals that the magnetization at saturation (Ms) for the Pt- and Ir-buffered films is higher than the usual Ms of CFA due to the proximity-induced magnetization (PIM) in Ir and Pt estimated to be 19% and 27%, respectively. The presence of PIM in these materials is confirmed using x-ray resonant magnetic reflectivity. Moreover, while no PIM is induced in W, higher PIM is obtained with Pt when it is used as a buffer layer rather than a capping layer. Brillouin light scattering in the Damon-Eshbach geometry is used to investigate the thickness dependences of the IDMI constants from the spin-wave nonreciprocity and the perpendicular anisotropy field versus the annealing temperature. The IDMI sign is found to be negative for Pt / CFA and Ir / CFA, while it is positive for W / CFA. The thickness dependence of the effective IDMI constant for stacks involving Pt and W shows the existence of two regimes similar to that of the perpendicular anisotropy constant due to the degradation of the interfaces as the CFA thickness approaches a critical thickness. The surface IDMI and anisotropy constants of each stack are determined for the thickest samples where a linear thickness dependence of the effective IDMI constant and the effective magnetization are observed. The interface anisotropy and IDMI constants investigated for the Pt / CFA / MgO system show different trends with the annealing temperature. The decrease of the IDMI constant with increasing annealing temperature is probably due to the electronic structure changes at the interfaces, while the increase of the interface anisotropy constant is coherent with the interface quality and disorder enhancement.

$\mathrm{C}{\mathrm{o}}_{2}\mathrm{FeAl}$ (CFA) ultrathin films, of various thicknesses $(0.9\phantom{\rule{0.28em}{0ex}}\mathrm{nm}\ensuremath{\le}{t}_{\mathrm{CFA}}\ensuremath{\le}1.8\phantom{\rule{4pt}{0ex}}\mathrm{nm})$, have been grown by sputtering on Si substrates, using Ir as a buffer layer. The magnetic properties of these structures have been studied by vibrating sample magnetometry (VSM), miscrostrip ferromagnetic resonance (MS-FMR), and Brillouin light scattering (BLS) in the Damon-Eshbach geometry. VSM characterizations show that films are mostly in-plane magnetized and the saturating field perpendicular to the film plane increases with decreasing CFA thickness suggesting the existence of a perpendicular interface anisotropy. The presence of a magnetic dead layer of 0.44 nm has been detected by VSM. The MS-FMR with the magnetic field applied perpendicularly to the film plane has been used to determine the gyromagnetic factor. The BLS measurements reveal a pronounced nonreciprocal spin wave propagation, due to the interfacial Dzyaloshinskii-Moriya interaction (DMI) induced by the Ir interface with CFA, which increases with decreasing CFA thickness. The DMI sign has been found to be the same (negative) as that of Pt/Co, in contrast to the ab initio calculation on Ir/Co, where it is found to be positive. The thickness dependence of the effective DMI constant shows the existence of two regimes similarly to that of the perpendicular anisotropy constant. The surface DMI constant ${D}_{s}$ was estimated to be $\ensuremath{-}0.37\phantom{\rule{0.16em}{0ex}}\mathrm{pJ}/\mathrm{m}$ for the thickest samples, where a linear thickness dependence of the effective DMI constant has been observed.

Co2FeAl (CFA) thin films of various thicknesses (1 nm $\le d \le 10$ nm) have been grown on (001) MgO single-crystal substrates and annealed at different temperatures ( $T_{a}$ ). Their magnetic properties have been studied by vibrating sample magnetometry, broadband microstrip ferromagnetic resonance (MS-FMR), and Brillouin light scattering (BLS). The effective magnetization, deduced from the fit of MS-FMR and BLS measurements, linearly decreases with the inverse thickness ( $1/d$ ) for all the annealing temperatures. This allows quantifying perpendicular surface anisotropy constants of 1.46, 1.71, and 1.29 erg/cm2 for $T_{a} = 215$ °C, 265 °C, and 315 °C, respectively. The perpendicular magnetization is achieved for the CFA films below a critical thickness that increases with increasing $T_{a}$ . Moreover, the fourfold anisotropy fields, measured in the in-plane magnetized films, increase with $T_{a}$ and decrease with respect to the CFA inverse thickness.

This study investigates chemically decorated surfaces as tools for the improvement of transport properties in superconducting YBa 2 Cu 3 O 7-x films. This approach, still to be thoroughly investigated, makes use of low-cost easily tunable chemical methods to obtain self-assembled oxide nanostructures on a substrate that will serve, in a second step, for the deposition of the superconducting film itself. The structures are supposed to produce in the superconducting matrix a specific amount of strain, which is generally held responsible for the increased transport capacity of variously doped samples. For the growth of the nanostructures, two different methods have been employed: polymer-assisted deposition and metal-organic decomposition (MOD). The main advantages and disadvantages of these two routes are discussed. The oxide chosen for the deposition is one commonly used for artificial pinning in YBa 2 Cu 3 O 7-x , namely Ba 2 YNbO 6 , together with the less common but highly interesting ferromagnetic compound La 0,77 Sr 0,33 MnO 3 . We also show how the density of these nanostructures can be easily controlled, and the necessary requirements for the growth of nanostructures are determined. A variety of crystalline substrates were tested for the deposition of the nanoparticles, such as SrTiO 3 , YSZ, MgO. YBa 2 Cu 3 O 7-x films have been deposited on selected samples via standard low-fluorine MOD and characterized scanning electron microscopy (SEM), x-ray diffraction (XRD), vibrating sample magnetometer (VSM), direct current (DC) resistivity, and critical current measurements. The presence of the nanostructures results, in this case, in a slight increased value of J c , which can be ascribed to the relatively low density of nanoparticles.

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Interface Dzyaloshinskii-Moriya interactions (iDMIs) in interlayer exchange coupled (IEC) Pt/${\mathrm{Co}}_{20}{\mathrm{Fe}}_{60}{\mathrm{B}}_{20}$(1.12 nm)/Ru/${\mathrm{Co}}_{20}{\mathrm{Fe}}_{60}{\mathrm{B}}_{20}$(1.12 nm) systems have been studied theoretically and experimentally. A vibrating sample magnetometer has been used to measure their magnetization at saturation and their interlayer exchange coupling constants. The latter are found to be of an antiferromagnetic nature for the investigated Ru range thickness ($0.5\text{--}1\phantom{\rule{0.16em}{0ex}}\mathrm{nm}$). Their dynamic magnetic properties were studied using the Brillouin light scattering (BLS) technique. The BLS measurements reveal pronounced nonreciprocal spin-wave propagation. In contrast to the calculations for symmetrical IEC CoFeB layers, this experimental nonreciprocity is Ru thickness and thus coupling strength dependent. Therefore, to explain the experimental behavior, a theoretical model based on the perpendicular interface anisotropy difference between the bottom and top CoFeB layers has been developed. We show that the Ru thickness dependence of the spin-wave nonreciprocity is well reproduced by considering a constant iDMI and different perpendicular interfacial anisotropy fields between the top and bottom CoFeB layers. This anisotropy difference has been confirmed by the investigation of the CoFeB thickness dependence of the effective magnetization of Pt/CoFeB/Ru and Ru/CoFeB/MgO individual layers, where a linear behavior has been observed.

Zn 1− x Co x O ( x ==0.05, 0.10, 0.15) nanoparticles have been synthesized by an alternative wet-chemical synthesis route using the SimAdd technique. The as-obtained powders were investigated by FT-IR spectroscopy, X-ray diffraction and thermal analysis correlated with evolved gas analysis (TG–DTA–FT-IR) in order to determine their chemical nature, crystalline structure and to establish the decomposition sequences. The precipitates are generally amorphous, but low-intensity reflection peaks assigned both to the zinc oxalate dihydrate, and zinc hydroxide can be observed in the recorded patterns, indicating that hydroxy-oxalate precipitates were obtained. The structure, morphology and magnetic properties of the thermally treated samples have been investigated by X-ray diffraction, FT-IR, HRTEM, SAED, UV–vis and EPR. XRD studies reveal a hexagonal wurtzite-type structure for all Zn 1− x Co x O samples. TEM investigations show particle size between 28 and 37 nm, with spherical and polyhedral shapes and with tendency to form aggregates. The presence of a Co 3 O 4 secondary phase was evidenced by XRD, UV–vis and EPR for the Zn 0.85 Co 0.15 O sample. The ferromagnetic behavior of the samples was revealed. The paper highlights that by varying the cobalt concentration it is possible to modulate the structural, morphological, optical and magnetic properties.

ZnO nanoparticles were synthesized by the precipitation method, with and without tetraethylammonium hydroxide (TEAH) addition. FTIR analysis was performed for the characterization of ZnO precursors. The as-obtained ZnO nanoparticles were analyzed by X-ray diffraction (XRD) and scanning and transmission electron microscopies (SEM/TEMs) in order to observe the structural and morphological properties of the samples. The ZnO sample, obtained from the precursor containing TEAH, thermally treated at 700 °C for 2 h, shows a compact structure with polygonal particles, having crystallites size around 42 nm. The correlation between morpho-structural characteristics and the optical properties of the as-obtained samples was mainly investigated.

Undoped and holmium-doped ZnO thin films were obtained, using the sol-gel method. The films were characterized by scanning electron microscopy (SEM), Hall effect measurements, electron paramagnetic resonance (EPR) spectroscopy and superconducting quantum interference device vibrating sample magnetometry (SQUID-VSM). The Hall effect measurements have indicated a n-type conduction with a resistivity of about 3.2 Ω.cm for the undoped ZnO and of about 4.5 Ω.cm for the 5 at. % Ho-doped ZnO thin films. The EPR measurements have indicated the presence of interstitial zinc in the undoped ZnO and the presence of zinc vacancies in 5 at. % Ho-doped ZnO. Ho (5 at. %)-doped ZnO films exhibit superparamagnetism at 5 K, while a low paramagnetic behavior was observed at room temperature.

Zinc oxide with a hexagonal wurzite type structure is an unique material that exhibits semiconducting, piezoelectric and pyroelectric properties. These properties play a key role for applications in optoelectronic devices. In the present work Al-doped and undoped ZnO films were obtained by soft chemistry starting with zinc acetate dihydrate and Al(III) isopropoxide in absolute ethyl alcohol. Trietanolamine was used as chelating agent. The films were deposited by dip coating technique on the silicon substrate and thermally treated at 500?C for one hour. The morphological characteristics of the films were investigated by Atomic Force Microscopy (AFM). Optical constants, such as refractive index (n) and extinction coefficient (k), were established by Spectroellipsometry measurements. Electrical conductivity of the studied films was determined in the 20-500?C temperature range by 'the four point method'. The morphology of the films is influenced by the starting sol composition, as found from AFM. According to the ellipsometric spectral data, more porous and thinner films, with smaller refractive index were obtained in the case of Al-doped ZnO films as compared with ZnO films. Both ZnO and Al-doped ZnO films presented high electrical receptivity. .

Brillouin light scattering (BLS), complemented by ferromagnetic resonance (FMR) characterization, has been used for studying spin-wave (SW) propagation in $\mathrm{Py}(L)/\mathrm{Pt}(6\text{\ensuremath{-}}\mathrm{nm})$ bilayers of various Py thicknesses $(4\phantom{\rule{0.16em}{0ex}}\mathrm{nm}\ensuremath{\le}L\ensuremath{\le}10\phantom{\rule{0.16em}{0ex}}\mathrm{nm})$. The FMR measurements allowed determination of the pertinent magnetic parameters and revealed the existence of a normal surface anisotropy. A pronounced asymmetry of Damon-Eshbach (DE) wave frequencies has been evidenced by BLS. Therefore, the difference between Stokes and anti-Stokes DE frequencies has been measured versus SW wave number for all the samples. A detailed discussion about the origin of this frequency difference is reported, which concludes that this is due to interface Dzyaloshinskii-Moriya interaction (IDMI).

10 nm and 50 nm thick Co 2 FeAl (CFA) thin films have been deposited on thermally oxidized Si(001) substrates by magnetron sputtering using a Tantalum cap layer and were then ex-situ annealed at 415°C, 515°C and 615°C during 15 minutes in vacuum. X-rays diffraction indicates that films CFA are polycrystalline and exhibit an in-plane isotropy growth. Ferromagnetic resonance measurements, using a microstrip line (MS-FMR), reveal a huge interfacial perpendicular magnetic anisotropy and small in-plane uniaxial anisotropy both annealing temperature-dependent. The MS-FMR data also allow concluding that the gyromagnetic factor remains constant and that the exchange stiffness constant increases with annealing temperature. Finally, the FMR linewidth decreases with increasing annealing temperature due to the enhancement of the chemical order, and allow deriving a very low intrinsic damping parameter (1.3×10 −3 at 615°C).

The correlation between magnetic and structural properties of Co_{2} FeAl (CFA) thin films of different thickness (10 nm, Comment: 5 pages, 4 figures, submitted to J. Mag. Mag. Mat

In the present paper, we analyze the role of in situ grown BaZrO3 (BZO) inclusions in YBa2Cu3O7−x (YBCO) thin films prepared by chemical solution deposition using a low fluorine coating solution, on the field angle dependence of the critical current density, J c (𝜃), data using the vortex path model. In order to form a coherent picture on the BZO doping influence on the pinning properties of the YBCO matrix, detailed structural analyses performed by X-ray diffraction techniques and microstructural evaluation by transmission electron microscopy are also presented. The evaluation of different contributions to the overall, J c , permitted us to prove the effectiveness of the BZO inclusions acting as isotropic pinning centers, reflected in a uniform component of high relative value with respect to other components. For the studied 10 mol % BZO doping concentration, a threefold increase in the critical current density, J c , of the YBCO host is measured, in self-field at 77 K, corresponding to a value of J c =2.9MA/cm2, whereas a factor 10 is measured at 1 T (J c =0.35 MA/cm2).

Bending effect on the magnetic anisotropy in 20 nm Co$_{2}$FeAl Heusler thin film grown on Kapton\textregistered{} has been studied by ferromagnetic resonance and glued on curved sample carrier with various radii. The results reported in this letter show that the magnetic anisotropy is drastically changed in this system by bending the thin films. This effect is attributed to the interfacial strain transmission from the substrate to the film and to the magnetoelastic behavior of the Co$_{2}$FeAl film. Moreover two approaches to determine the in-plane magnetostriction coefficient of the film, leading to a value that is close to $\lambda^{CFA}=14\times10^{-6}$, have been proposed., Comment: 4 pages, 4 figures

Co2FeAl (CFA) thin films with thickness varying from 10 nm to 115 nm have been deposited on MgO(001) substrates by magnetron sputtering and then capped by Ta or Cr layer. X-rays diffraction (XRD) revealed that the cubic $[001]$ CFA axis is normal to the substrate and that all the CFA films exhibit full epitaxial growth. The chemical order varies from the $B2$ phase to the $A2$ phase when decreasing the thickness. Magneto-optical Kerr effect (MOKE) and vibrating sample magnetometer measurements show that, depending on the field orientation, one or two-step switchings occur. Moreover, the films present a quadratic MOKE signal increasing with the CFA thickness, due to the increasing chemical order. Ferromagnetic resonance, MOKE transverse bias initial inverse susceptibility and torque (TBIIST) measurements reveal that the in-plane anisotropy results from the superposition of a uniaxial and of a fourfold symmetry term. The fourfold anisotropy is in accord with the crystal structure of the samples and is correlated to the biaxial strain and to the chemical order present in the films. In addition, a large negative perpendicular uniaxial anisotropy is observed. Frequency and angular dependences of the FMR linewidth show two magnon scattering and mosaicity contributions, which depend on the CFA thickness. A Gilbert damping coefficient as low as 0.0011 is found., 11 pages, 11 figures, to appear in Phys. Rev B

10 nm and 50 nm Co$_{2}$FeAl (CFA) thin films have been deposited on MgO(001) and Si(001) substrates by magnetron sputtering and annealed at different temperatures. X-rays diffraction revealed polycrystalline or epitaxial growth (according to the relation CFA(001)[110]//MgO(001)[100] epitaxial relation), respectively for CFA films grown on a Si and on a MgO substrate. For these later, the chemical order varies from the A2 phase to the B2 phase when increasing the annealing temperature (Ta) while only the A2 disorder type has been observed for CFA grown on Si. Microstrip ferromagnetic resonance (MS-FMR) measurements revealed that the in-plane anisotropy results from the superposition of a uniaxial and of a fourfold symmetry term for CFA grown on MgO substrates. This fourfold anisotropy, which disappears completely for samples grown on Si, is in accord with the crystal structure of the samples. The fourfold anisotropy field decreases when increasing Ta while the uniaxial anisotropy field is nearly unaffected by Ta within the investigated range. The MS-FMR data also allow for concluding that the gyromagnetic factor remains constant and that the exchange stiffness constant increases with $T_{a}$. Finally, the FMR linewidth decreases when increasing Ta, due to the enhancement of the chemical order. We derive a very low intrinsic damping parameter (1.3*10^-3 and 1.1*10^-3 for films of 50 nm thickness annealed at 615 {\deg}C grown on MgO and on Si, respectively)., Comment: 8 pages, 7 figures to appear in J. App. Phys

This work reports on the structural and morphological characterization of ceria thin films grown by chemical solution deposition (CSD) techniques. The coating solution was prepared starting from cerium 2,4-pentadionate, Ce(CH3COCHCOCH3)3, and propionic acid, C2H5COOH, further concentrated by distillation. The as-prepared solution was spin coated on single crystalline (100) SrTiO3 (STO) substrates. The precursor films were heat treated in air at 900°C both by a rapid heating and quenching to room temperature (A) and annealing (B). The X-ray structural analysis and the SEM and AFM morphological analysis for the CeO2/STO thin film have revealed the influence of the thermal treatment on the growth mechanism. The as-obtained polycrystalline nanostructured ceria thin films present an average grain size of 40–50 nm and a roughness of 1.5–5.4 nm, depending on the thermal treatment. The annealing renders the ceria thin film a smoother surface with respect to the rapid heat treatment followed by quenching, performed both at the same temperature.

This work reports on the preparation of a BaZrO3 (BZO) nanopowder by the chemical decomposition of an oxalate precursor starting from barium acetate and zirconium oxychloride. The X-ray peak profile analyses and the scanning electron microscopy (SEM) have indicated that the mean powder size ranges from 30nm to 340 nm for the thermal treatment temperature varying from 700°C to 1200°C, respectivelly. The as prepared powder has been used to manufacture YBCO-5 mol. % BZO composite targets from which epitaxial YBCO thin films on (100)SrTiO3 substrate were ablated. The X-ray analysis have revealed that the BZO nanoislands are epitaxially grown throughout the YBCO film, having the same epitaxial relationship as YBCO. Moreover, as revealed by SEM, the presence of BZO considerably improves the morphology of the YBCO film. The critical temperature (Tc) registered a slight decrease with the BZO concentration. Nevertheless, the BZO addition resulted in an improvement of the critical current density, Jc. The JcvsB curve exihibits a large plateau extended up to about 2.5 Tesla. The YBCO-BZO composite films showed pinning forces with a c-axis correlated character, as revealed by the angular behaviour of Jc.