Magnetic Properties Of Films Research Articles

Effect of Mn doping on the structural, optical, and magnetic properties of In2O3 films

(In1−xMnx)2O3 films were grown by radio frequency-magnetron sputtering technique. Effect of Mn doping on the structural, optical, and magnetic properties of films is investigated systematically. The detailed structure analyses suggest that Mn ions substitute for In3+ sites of the In2O3 lattice in the valence of +2 states, and Mn-related secondary phases or clusters as the source of ferromagnetism is safely ruled out. All films show typical room temperature ferromagnetism. The saturation magnetization Ms increases first, and then decreases, while carrier concentration nc decreases monotonically with Mn doping, implying that the ferromagnetism is not directly induced by the mediated carriers. The optical bandgap Eg of films decreases monotonically with the increase of Mn concentration, and there exists a linear functional dependence between Eg and nc2/3, which is consistent with Burstein-Moss shift arguments. It can be concluded that the ferromagnetic order in Mn-doped In2O3 films is intrinsic, arising from Mn atoms substitution for the In sites of In2O3 lattice. The oxygen vacancies play a mediation role on the ferromagnetic couplings between the Mn ions.

Strain Effect on Magneto-optical and Magnetic Properties of Film System Based on Fe and Pt

In the work the strain effect in magneto-optical (magneto-optical Kerr effect - MOKE) and magnetic properties of thin films and multilayers based on Fe and Pt in unstrained and strained states was studied. The proposed ratio for strain coefficient of MOKE us quantitative characteric this effect. By measuring the Kerr angle for different values of strain and geometry measurements, it is concluded the influence of strain effects on magnetic characteristics of two-layer films and multilayers.

Influence of substrate on the high-frequency permeability of thin iron films

The ferromagnetic resonance (FMR) spectra of thin metallic films obtained by magnetron deposition on polymeric and ceramic substrates are investigated in the strip line at frequencies of 0.13–12 GHz via frequency and external magnetic field sweeping. The influence of mechanical stresses on the FMR spectra of films deposited on an elastic (polyethylene rephthalate) substrate is discussed. The magnetostriction contribution to the anisotropy field of a film, as well as the influence of tensile stresses on the quasi-static permeability and FMR frequency, is estimated. It is demonstrated that the microwave properties of a thin metallic film are also specified by the properties of the substrate with such a film. A distinction in the magnetic properties of films with the same composition, which are deposited on different substrates, is explained in terms of the magnetostriction effect.

3D like vortex behavior and the thermally activated flux flow mechanism in (Hg0.8Re0.2)Ba2Ca2Cu3Ox superconducting films

Approximately 1 μm thick high quality epitaxial c-axis oriented (Hg0.8Re0.2)Ba2Ca2Cu3Ox superconducting films have been prepared on MgO (100) substrates using spraying technique and post-Hg-Vapor annealing. The effect of the heating temperature–time combinations and the filling factor of Hg (ffHg) on the physical, electrical and magnetic properties of the thick films have been investigated. The XRD investigations showed that the a–b plane of HgRe-1223 phase align parallel to the substrate surface. The best Tc and Tzero were found to be 130.6 and 127.2 K, respectively. The superconducting transition of the films has been measured under applied magnetic field up to 6 T. The results obtained suggested that dissipative resistivity can be explained by thermally activated flux motion below critical temperature under applied magnetic field. The temperature and field dependences of the activation energy in the thermally activated flux flow region have also been investigated. The calculated values of m and α values were found to be 1.42–1.49 and 0.498–0.518 respectively and suggesting a 3D like behavior and the thermally activated flux flow mechanism for all films fabricated. Magnetic properties of the films up to 6 T have also been investigated. The calculated value of critical current density, Jc, was found to be 4.7 × 106 A/cm2 at 10 K for the optimally treated films.

Structural, optical and magnetic properties of Fe-doped barium stannate thin films grown by PLD

Barium stannate is a wide band gap semiconductor with cubic perovskite structure. Polycrystalline bulk samples of BaSn1−xFexO3d (BFS), with x=0.00, 0.02, 0.03, 0.05 and 0.10 were prepared by solid-state reaction. In this paper, we report the growth of undoped and Fe doped barium stannate thin films on fused silica substrate using pulsed laser deposition (PLD) technique at a relatively high substrate temperature and low oxygen pressure. The deposited films have wide bandgap and are transparent in the visible region. The X-ray diffraction analysis of the films confirmed the cubic structure. Microstructural studies were carried out using micro-Raman spectroscopy and AFM analysis. Defect induced Raman shifts were observed in the samples. Magnetic studies revealed an increase in magnetic properties for films doped with 10at% Fe doped samples.

Magnetic properties of MnAs thin films irradiated with highly charged ions

We present the first investigation on the effect of highly charged ion bombardment on a manganese arsenide thin film. The MnAs films, 150nm thick, are irradiated with 90keV Ne9+ions with a fluence varying from 1.6×1012 to 1.6×1015ions/cm2. The structural and magnetic properties of the film after irradiation are investigated using different techniques, namely, X-ray diffraction and magnetic force microscope. Preliminary results are presented. From the study of the lattice spacing, we measure a change on the film structure that depends on the fluence, similarly to previous studies with other materials. On the other hand, investigations on the surface show a strong modification of its magnetic properties.

Reducing the writing field of L1-FePt by graded order parameter

The dependence of the magnetic properties of epitaxial Fe50Pt50 films on order parameter (S) was investigated. It was demonstrated that the magnetic anisotropy could be tuned by controlling S which can be controlled by the growth temperature. Based on this result, two kinds of multilayered structures, each with a 13 nm fully ordered Fe50Pt50 layer as the bottom layer, were built: (1) 4-layered structure with S decreasing layer by layer from bottom to top; (2) graded structure with S changing more continuously along the thickness. The magnetic properties of the films were characterized using vibrating sample magnetometry. It was found that both structures have their easy axis perpendicular to the film; the anisotropy fields of the 4-layered film and the graded film are 53 kOe and 37 kOe, respectively. These values are much lower than that of the fully ordered uniform Fe50Pt50 film (about 73 kOe). The results suggest that it may be possible to reduce the writing field of Fe50Pt50 by gradually changing the order parameter.

Structural, optical and magnetic properties of Mn-doped ZnO thin films prepared by sol–gel method

Undoped and Mn-doped ZnO thin films were prepared on quartz glass and Si(100) substrates by the sol–gel method at room temperature, and the effects of Mn content on the structural, optical, and magnetic properties of these films were investigated. X-ray diffraction patterns reveal that all the films are single phase and have wurtzite structure with (002) preferential orientation along c-axis, indicating there are not any secondary phases. X-ray photoelectron spectroscopy patterns suggest that Mn2+ ions were successfully incorporated into the lattice position of Zn2+ ions in ZnO host. Optical transmittances of the films were recorded in the wavelength range of 300–800nm, and the band gaps of the films were determined. As the content of Mn increases, the crystallite size and the optical band gap of the films decrease while the crystalline quality deteriorates gradually. The intensity of photoluminescence spectra is suppressed with Mn doping. Magnetic measurements indicated that undoped ZnO was diamagnetic in nature whereas Mn-doped ZnO samples exhibited ferromagnetic behavior at room temperature, which is possibly related to the substitution of Mn2+ ions for Zn2+ ions in the ZnO lattice. It is also found that the Mn doping content can affect the ferromagnetic behavior of the films effectively.

Thickness dependence of surface roughness and magnetic properties of FeNiCr thin films

In order to apply FeNiCr ternary alloy thin films for magnetic machine-readable devices, the thickness effects on the surface roughness and magnetic properties of these films have been studied. The surface roughness of FeNiCr increased from 0.77nm to a maximum value of 2.16nm as the film thickness was increased from 33 to 103nm, and then decreased to 1.75nm as the film thickness was further increased to 189nm. The coercivity of FeNiCr films changes with the film thickness in a similar way as surface roughness. The in-plane coercivity of FeNiCr increased from 27.3Oe to a maximum value of 60.1Oe as the film thickness was increased from 33 to 103nm, and then decreased to 10.4Oe as the film thickness was further increased to 189nm.

Magneto-optical properties of cerium substituted yttrium iron garnet films with reduced thermal budget for monolithic photonic integrated circuits

Thin films of polycrystalline cerium substituted yttrium iron garnet (CeYIG) were grown on an yttrium iron garnet (YIG) seed layer on Si and Si-on-insulator substrates by pulsed laser deposition, and their optical and magneto-optical properties in the near-IR region were measured. A YIG seed layer of ~30 nm thick processed by rapid thermal anneal at 800°C provided a virtual substrate to promote crystallization of the CeYIG. The effect of the thermal budget of the YIG/CeYIG growth process on the film structure, magnetic and magnetooptical properties was determined.

Dependence of the microstructure and magnetic properties of amorphous TbFeCo films on the type and pressure of the gas in sputtering

Amorphous Tb30Fe60Co10 films have been fabricated by magnetron sputtering. The dependences of the microstructure and magnetic properties of these films on the type and pressure of the gas in the sputtering chamber have been studied. The pressure of the Ar, Kr, and Xe gases used in the experiments is varied in the sputtering chamber from 0.01 to 4.00 Pa. It has been established that sputtering in the heavy gas (Kr) conducted within the pressure range covered does not permit fabricating TbFeCo films with the easy magnetization axis perpendicular to the film plane. With Xe used at pressures below 1.0 Pa, one observes in TbFeCo films an increase of the coercivity, with the hysteresis loop approaching rectangular shape. Sputtering and deposition in Ar at a pressure of ∼0.67 Pa result in the formation of amorphous Tb30Fe60Co10 films with magnetic characteristics satisfying the requirements imposed upon information carriers intended to be employed in perpendicular recording. It has been demonstrated that, by magnetron sputtering in an Ar atmosphere performed at pressures below 1 Pa, one can produce amorphous Tb30Fe60Co10 films suitable for magneto-optical ultra-high-density information recording.

Magnetic Properties and Magnetic Domain Structures Evolution Modulated by CoFeB Layer in [Pd/Co]/CoFeB/MgO/CoFeB/[Co/Pd] Perpendicular MTJ Films

A series of MgO perpendicular magnetic tunneling junction (p-MTJ) films with soft/hard composite electrodes is prepared by RF-sputtering, where amorphous CoFeB is chosen as soft layer. The modulation of MTJs film magnetic properties on CoFeB thickness is investigated. The critical thickness for composite free layer transform from rigid magnet (RM) to exchange spring system (ES) is indentified. Besides, an unexpected in-plane exchange bias is observed which is attributed to the formation of closure domains. The evolution of domain structures on CoFeB is examined by magnetic force microscope. Coexistence of two distinguished magnetic domains of different sizes is observed. It is found that the evolution of domain morphology as varying CoFeB thickness is due to the modulation of effective anisotropy.

Structural and magnetic properties of La2NiMnO6 thin films on LaAlO3 substrate with varying thickness

In the present work, the effect of film thickness on the structural and magnetic properties of La2NiMnO6 (LNMO) ferromagnetic double perovskite thin films has been systematically investigated. LNMO thin films of varying thickness from 54nm to 256nm were deposited using the pulsed laser deposition technique onto single-crystalline LaAlO3 substrate. The X-ray diffraction pattern and Raman scattering observations reveal that all films have c-axis epitaxial growth and an orthorhombic structure. The Raman spectra of the films are dominated by two broad peaks at around 534cm−1 and 676cm−1 assigned to the antisymmetric stretching (AS) and symmetric stretching (S) vibrations of the octahedra, respectively. The Raman peaks of the LNMO thin films are blue shifted in comparison to those of bulk LNMO and the shift increases with decreasing film thickness, indicating the increased influence of strain. The critical thickness for strain relaxation, as determined from the Raman spectra, is between 110nm and 156nm. However, the strain is observed to have large effect on the magnetic properties of films. Ferromagnetic to paramagnetic transition temperature (Tc) and the saturation magnetization were found to increase with increase in the film thickness. The film with thickness of 256nm exhibits a saturation magnetic moment of 4.5μB/f.u. and coercive field of 630Oe at 10K, with a Curie temperature close to 280K.

Microstructure and magnetic properties of Ni3Fe solid solution thin films deposited by DC-magnetron sputtering

Fe–Ni thin films were co-sputter deposited from Ni and Fe metallic targets on different substrates. The evolution of the coating composition as a function of the discharge current dissipated on each target is studied and the targeted composition for Ni3Fe is obtained by fixing the discharge current applied on Fe target at 0.5A and adjusting the discharge current applied on Ni target at 0.45A. The as deposited coating with convenient composition presents a disordered solid solution FCC structure. Finally, the magnetic properties of the films are investigated as a function of their thickness. We have observed that coercivity decreases slightly and magnetic moment increases which increasing film thickness.

Effects of deposition temperature and in-situ annealing time on structure and magnetic properties of (001) orientation FePt films

FePt films were prepared on (100) oriented single crystal MgO substrates at high temperature ranging from 620 until 800°C and in-situ annealed for different times ranging from 0 to 60min to obtain ordered FePt films. The structural analysis indicates that FePt films grow epitaxially on MgO (100) substrates. Both increasing deposition temperature and in-situ annealing time enhance the (001) texture and ordering of FePt films. The magnetic analysis shows that these L10 FePt films have perpendicular anisotropy and the easy magnetization c-axis is perpendicular to the film plane. Magnetization reversal is controlled by a rotational mechanism. The hard magnetic properties of the films are improved with increasing deposition temperature or in-situ annealing time.

Strain dependent stabilization of metallic paramagnetic state in epitaxial NdNiO3 thin films

We report here the strain dependent study of epitaxial NdNiO3 films deposited on LaAlO3 and SrTiO3 substrates using pulsed laser deposition. Electrical transport and magnetic properties of films are found to be controlled by the substrate induced strain. NdNiO3 film on SrTiO3 substrate exhibits behaviour similar to that of bulk NdNiO3, while stabilization of low temperature metallic paramagnetic phase has been observed for film deposited on LaAlO3 substrate. Invariance of Raman spectra, with temperature, of the film on LaAlO3 reveals that the melting of charge ordering under compressive strain is responsible for the stabilization of metallic phase at lower temperature.

Effect of Ag underlayer thickness on the microstructure and magnetic properties of L10-FePt films

FePt/Ag films were deposited on thermally oxidized Si(100) substrates by magnetron sputtering at room temperature and then the as-deposited films were annealed at 500 ∘C. The microstructure and magnetic properties of the films have been investigated by X-ray diffraction and vibrating sample magnetometry. The results indicate that introduction of the Ag underlayer promotes an ordering transformation of the FePt phase due to thermal tensile stress between the Ag underlayer and the FePt film. The in-plane tensile stress induced by the Ag underlayer should stretch the horizontal lattice parameter of FePt; thus, it is helpful for the ordering transformation. With increasing Ag underlayer thickness, the ordering parameter and coercivity first increase and then decrease. When the Ag underlayer thickness is 12 nm, the ordering parameter and coercivity of the film reach the maximum values, respectively. The Ag underlayer thickness also affects the magnetization reversal mechanism.

Microstructure and Magnetic Properties of the CoTiO2 Thin Films

Co (t nm)/TiO2(200 nm) films were prepared by DC facing-target magnetron reactive sputtering system onto glass substrates at room temperature. The influence of the Co distribution on microstructure and magnetic properties of films was investigated in detail. The results indicate that CoTiO2thin films with t= 2 nm island-type deposited showed a homogeneous structure, and pure ferromagnetic properties of thin films are only attributed to the CoTiO2phases. On the other hand, in case of thin films above t= 2nm, the overall ferromagnetic properties depended on both CoTiO2and CoTi phases.

Correlation between electronic structure and magnetic properties of Fe-doped ZnO films

Fe-doped ZnO films with different Fe concentrations that display ferromagnetism at room temperature have been prepared by plasma assisted molecular beam epitaxy (p-MBE) techniques. Synchrotron-based measurements of photoemission spectroscopy (PES), x-ray absorption spectroscopy (XAS), resonant photoemission spectroscopy (RPES), and superconducting quantum interference device (SQUID) were performed to investigate the electronic structure and magnetic properties of the films. It was found by Fe 2p PES and XAS that the dominant valence state of Fe ions is Fe3+ and that the configuration of Fe ions varies from tetrahedral sites to octahedral sites as the Fe concentration increases. Results of RPES indicate that the electronic states related to Fe2+ also exist near the Fermi level and that the distribution of Fe 3d electronic states in the valence band varies with different Fe concentrations. Correlations of the magnetic properties with the electronic structure of Fe-ZnO films have established that the electronic states related to Fe2+ and localized defects like Zn vacancies play an important role for ferromagnetism of Fe-ZnO films, while Fe3+ ions at octahedral sites destabilize the ferromagnetic interactions.

Ferromodulation Effect Usage for the Magnetic Film Anisotropy Investigation

The ferromodulation effect response model of an anisotropic soft magnetic film placed in the crossed permanent bias and alternating excitation magnetic fields is built. It was shown theoretically and experimentally how such a field configuration can be used for registering the effects relating to the film magnetic anisotropy properties.