FeSi Film Research Articles

Effect of Cr interlayers on texture and magnetic properties of FeSi films with micrometer thickness

Magnetised soft ferromagnetic films with micrometer thicknesses can be used as π-flippers in spin-echo small-angle neutron scattering instruments. An FeSi film with a total thickness of 2000 nm separated by Cr interlayers (each 10 nm thick) was fabricated using direct-current magnetron sputtering. The thickness of each FeSi layer was 100 nm between adjacent Cr interlayers. Hysteresis loop measurements were performed to characterise the magnetic properties of the FeSi films. X-ray diffraction measurements, high-resolution transmission electron microscopy, and selected-area electron diffraction were used to characterise the texture. Results demonstrated that the saturation magnetisation of the FeSi film separated by Cr interlayers was higher and its coercivity was lower than those of the FeSi film separated by Ta interlayers because of different texture of FeSi layer. The FeSi film separated by Cr interlayers featured FeSi (210) and FeSi (221), and the Cr interlayers presented Cr (110). The FeSi layer between the Cr interlayers demonstrated structural coherency with the upper FeSi layer, and continuity of the lattice fringes from the Cr grains to the FeSi layers was observed. Therefore, degradation in the soft magnetic properties of FeSi films can be prevented by the insertion of Cr interlayers.

Effect of Ta Interlayers on Texture and Magnetic Properties of FeSi Films with Micrometer Thickness.

Magnetized soft ferromagnetic films with micrometer thickness were studied. A FeSi film, with a total thickness of 2000 nm, separated by 10 nm-thick Ta interlayers, was fabricated using the direct-current magnetron sputtering technique. The thickness of each FeSi layer between adjacent Ta layers was 100 nm. Hysteresis loop measurement was used to characterize the magnetic properties of the layer. X-ray diffraction patterns and high-resolution transmission electron microscopy were used to characterize its texture. The experimental results showed that the FeSi film separated by Ta interlayers exhibited a lower saturation magnetization and a higher coercivity than those of the 1140 nm-thick FeSi film. The insertion of Ta interlayers resulted in the disappearance of the crystal plane of FeSi (221), and better texture of the crystal plane of FeSi (210). The FeSi film exhibited a crystal plane of FeSi (210) with a bcc crystalline structure. The Ta interlayers were partially amorphous, exhibiting crystal plane of Ta (002) and TaSi2 (310). The matching of magnetic properties between interlayers and soft magnetic layers played an important role in maintaining its soft magnetic properties.

Magnetized FeSi film with micrometer thickness inserted with Cr layers as [formula omitted]-flippers for neutron spin-echo spectrometry

Magnetized soft ferromagnetic films with micrometer thickness can be used as π-flippers for a spin echo small-angle neutron scattering (SESANS) instrument. Two FeSi monolayers and two FeSi/Cr multilayers were fabricated using a direct-current magnetron sputtering technique. The thicknesses of the two FeSi monolayers were 114 nm and 1140 nm, respectively. The two FeSi/Cr multilayers with 2 and 20 periods, respectively, were composed of FeSi layers having thicknesses of 1000 nm and 100 nm, respectively, and 10 nm-thick Cr layers. Hysteresis loop measurements and X-ray diffraction measurements were used to characterize their magnetic properties and texture, respectively. Polarized neutron flipping efficiency measurements were conducted using the TPNR (Time-of-flight and Polarized Neutron Reflectometer) to determine the flipping efficiency of the FeSi/Cr multilayer with [100 nm FeSi/10 nm Cr]20. The experimental results show that the saturation magnetization of the FeSi-monolayers decreased and the coercivity increased as their thickness increased. The FeSi/Cr multilayer with [100 nm FeSi/10 nm Cr]20 had higher saturation magnetization (1300 emu/cm 3) and lower coercivity than those of [1000 nm FeSi/10 nm Cr]2, although the total thickness of the FeSi layers was almost the same, and its maximum flipping efficiency was up to 98% for polarized neutrons.

Magnetized Fesi Film with Micrometer Thickness Inserted with Cr Layers as Π-Flippers for Neutron Spin-Echo Spectrometry

Magnetized Fesi Film with Micrometer Thickness Inserted with Cr Layers as Π-Flippers for Neutron Spin-Echo Spectrometry

Observing the magnetization reversal processes and anisotropic effective damping of epitaxial FeSi/MgO (001)

Epitaxial FeSi film on MgO (001) substrate was fabricated via a radio frequency magnetron sputtering technology. The epitaxial relationship of FeSi(001)/[110]//MgO(001)/[100] was characterized by crystal structure measurements and confirmed by in-plane biaxial magnetic anisotropy through vibrating sample magnetometer (VSM). By measuring Kerr magnetic hysteresis loops and recording the real-time magnetic domain images through surface magneto-optic Kerr effect (MOKE), two successive 90° domain wall displacement along easy axis and two discontinuous 90° domain wall displacement along hard axis were directly observed. Meanwhile, the difference of magnetic hysteresis loops obtained by VSM and MOKE devices were discussed. Furthermore, from the results of magnetic field sweeping ferromagnetic resonance measurements, it was found that FeSi film possesses an anisotropic effective damping constant of 0.0042 for easy axis direction and 0.0053 for hard axis direction, which was ascribed to the crystallographic defects induced two magnon scattering contributions.

Non-Volatile Regulation of Magnetism via Electric Fields in Polycrystal FeSi/(011) PMN-0.32PT Heterostructures

The choice and configuration of the ferroelectric (FE) substrate and the ferromagnetic (FM) layer in FM/FE heterostructures play an important role in magnetism modification with regard to amplitude and efficiency. In this study, we fabricated FeSi films on low crystalline (011) [Pb(Mg1/3Nb2/3)O3]0.7-[PbTiO3]0.3 (PMN-0.32PT) using radio frequency magnetron sputtering. In the annealed FeSi/(011) PMN-0.32PT heterostructures, the FeSi film presented with a (011) preferred orientated polycrystalline structure and low magnetocrystalline anisotropy. Both loop-like and butterfly-like magnetism modifications were observed by applying bipolar electric fields, and the weak and abnormal electrically mediated magnetism behaviors were significantly different from the prominent magnetic anisotropy transition in FeSi/(011) PMN-0.3PT. The comparative analyses suggest that the resulting high-quality single-crystalline PMN-xPT and FM films with low coercivity are of great significance for exploring giant, reversible, and non-volatile magnetism regulation.

Effects of adding elements M (M = C, B, Mn, Al and Al + Co) on stability of amorphous semiconducting Fe–Si films

Amorphous semiconducting Fe–Si film with direct optical band gap (Eg) has become a promising candidate material for optoelectronic devices. It can avoid the difficulties of crystalline materials preparation. The key to expanding its applications is to further improve its stability under the premise of maintaining the semiconducting performance. In the present paper, the amorphous Fe–Si–M (M = C, B, Mn, Al, Al + Co) films were prepared on the single-crystal Si(100) and Al2O3(0001) substrates by radio frequency (RF) magnetron sputtering to discuss the effects of the third (fourth) elements M on the films’ performance. The result shows that all the added elements except for Al have no obvious effects on the Eg of the amorphous Fe–Si films. The amorphous Fe–Si–M and Fe–Si films have the same variation trends on the electrical resistivity (ρ). However, the conductivity of the films slightly increase after adding the third (fourth) elements. Both the theoretical calculation and experimental results show that the third element C, B and Al can significantly improve the amorphous stability, and the initial crystallization temperatures (Tx) of the films increase with the third element content. Particularly, the Tx of amorphous Fe–Si–C films are over 500 °C, the highest Tx is up to 581 °C, which is ~ 100 °C above that of the a-Fe–Si film with the same Fe content. Therefore, to select the added element M and its content properly can greatly improve the stability of the film without significant effect on the Eg and ρ of the amorphous Fe–Si–M films.

Electric field modulation of reversible and non-volatile magnetic anisotropy transition in (0 1 1) 0.7[Pb(Mg1/3Nb2/3)O3]–0.3[PbTi0.3O3]/FeSi heterostructures

Electric-field-modulated magnetic properties are investigated on FeSi films with a (0 1 1) preferred orientation on (0 1 1) 0.7[Pb(Mg1/3Nb2/3)O3]–0.3[PbTi0.3O3] (PMN–0.3PT) single crystal substrates. When saturated and reversed coercive electric fields are alternately applied to the Pt/PMN–0.3PT/FeSi/Ta heterostructures, a reversible and non-volatile magnetic transition between four-fold and two-fold anisotropy is demonstrated by means of the angular dependence of remanent magnetization measurements. Based on the electric field control of the 90° magnetic easy axis direction transition of the FeSi film, we also achieve electric-field-mediated giant 180° magnetization switching with the assistance of the magnetic field pulse.

Rod-like precipitates formed in vapor-deposited Fe-Si film

Rod-like precipitates formed in vapor-deposited Fe-Si film

Electric field induced magnetic anisotropy transition from fourfold to twofold symmetry in (001) 0.68Pb(Mg1/3Nb2/3)O3-0.32PbTiO3/Fe0.86Si0.14 epitaxial heterostructures

The epitaxial growth of FeSi film on (001) 0.68Pb(Mg1/3Nb2/3)O3-0.32PbTiO3 (PMN-0.32PT) was fabricated by sputtering and confirmed by high-resolution transmission electron microscopy. A fourfold symmetric angular remanent magnetization curve of as-deposited FeSi thin film is well fitted theoretically by considering the cubic magnetocrystalline anisotropy. We found that the fourfold anisotropy decreases slightly when an electric field (E) is applied on the Pt/PMN-0.32PT/FeSi/Ta heterostructures with Pt layer as the positive electrode. However, a magnetic anisotropy transition from fourfold anisotropy to twofold anisotropy occurs under negative E. The strain-electric field curve suggests that the observed different variation trend of magnetic anisotropy results from the asymmetric strain response on the polarity of E. Moreover, once the transition happens, it was irreversible unless the heterostructures are heated above the phase transition temperature of PMN-0.32PT.

Formation of Silicon and Silicon-Based Semiconductor Materials via Photoinduced Reaction Using Femtosecond Laser

ABSTRACTWe have succeeded in silicon (Si) precipitation inside a glass/aluminum (Al) sandwich structure via photoinduced reaction using femtosecond (fs) laser irradiation. The sandwich structure was fabricated by direct bonding below 573 K. Raman spectra at the photomodified area indicated that Si crystals formed at the interface between the glass and metallic Al after the laser irradiation. In addition, the particle size of the precipitated Si could be changed by changing the pulse energy of the laser. Furthermore, we have also focused the laser pulses on Fe-Si film to trigger crystallization and phase transformation of FexSiy at the interface between Fe/Si multilayer and glass.

Ab initio computer simulation of adsorption of a Fe monolayer on Si(111)

Computer simulation of adsorption of an Fe monolayer on Si(111) is carried out in the generalized gradient approximation in the density functional theory. It is shown that mixing of Fe and Si atoms followed by the replacement of Si atoms and the formation of a silicide-like film containing two types of domains (with the A8 and B8 structure) takes place in the course of deposition. Analysis of the atomic structure of this compound shows that the formation of this interface makes it possible to obtain an FeSi film (with the CsCl-type structure) as well as FeSi2 film (with a CaF2-type structure).

Magnetic ordering of the Fe/Si interface and its initial formation

High-resolution photoelectron spectroscopy with synchrotron radiation and magnetic linear dichroism in Fe 3p core-level photoemission has been used to study both the initial stages of Fe/Si(111)7×7 and Fe/Si(100)2×1 interface formation and their ferromagnetic ordering. The correlation between the phase composition, electronic structure, and magnetic behavior of the interfaces has been established. It is shown that in-plane ferromagnetic ordering of the interfaces has a threshold nature and arises after the deposition of ∼7 Å Fe in both systems. However, the remanent magnetization of Fe/Si(111) is greater than that of Fe/Si(100) due to the difference in the chemistry of the phases being formed. In the former case, it was found that at room temperature an ultrathin metastable FeSi film with the CsCl structure grows at the first stage of Fe deposition on Si. At higher Fe coverages, a Si solid solution in iron, and later an Fe film, is found to develop on FeSi. The magnetic properties of the solid solution and the Fe film of ∼15 Å thick are quite similar. At the Fe/Si(100) interface, we observe the formation of iron-rich Fe3Si, in which the average magnetic moment of Fe atoms is markedly lower than that of the Fe film. Solid-phase reactions, starting at ∼100 °C in both systems, lead to a gradual conversion of ferromagnetic phases to the nonmagnetic ε-FeSi phase, which transforms to β-FeSi2 at temperatures above 600 °C.

Reaction of Iron with Amorphous Silicon and Crystal Silicon for the Fabrication of Iron Silicides

Iron silicide films with two different structures were fabricated by electron beam evaporation (EBE) technique. X-ray diffraction (XRD), Fourier transform infrared (FTIR) and scanning electron microscope (SEM) were carried out to describe the characteristics and structures of the films. It was found that after annealing at 800oC for 5 h, the β-FeSi2 film formed in the sample with the structure of Si/Fe film on silicon substrate, while only FeSi film generated in the sample with the structure of Si/Fe/Si films on silicon substrate. It is considered that the different iron silicides may be due to the different reaction of iron with crystal silicon or amorphous silicon, which is related to diffusion of iron or silicon atoms.

Mn – Ir ∕ Fe – Si exchange-coupled multilayer film with plural ferromagnetic resonance absorptions for wideband noise filter

Mn – Ir ∕ Fe – Si exchange-coupled multilayer films for a wideband and gigahertz band noise filters are fabricated and evaluated. The Fe–Si film has characteristics of high saturation magnetization of 19kG, low magnetostriction of the order of 10−6, and high resistivity of 73μΩcm. When the exchange bias magnetic field is introduced to the Fe–Si layers by the effect of Mn–Ir∕Fe–Si exchange-coupling, the ferromagnetic resonance (FMR) frequency of the multilayer film is higher than the natural frequency of the single Fe–Si film. In addition, the multilayer film which has different thicknesses in each Fe–Si layer has plural FMR frequencies. The multiple FMR frequency gives the film characteristic of wideband energy absorption. The FMR absorption bandwidth of the multilayer film which has three FMR frequencies is about three times wider than that of a single FMR film. Therefore, the multilayer film with plural FMR frequencies has an advantage in wideband noise absorption and will be a useful material for the wideband and gigahertz frequency range noise filterings.

Fe-Si磁性膜に及ぼすRu下地層の効果

The Fe-Si magnetic film with an Ru underlayer was fabricated and characterized. In the film, the Fe-Si grain became small when using a very thin Ru underlayer. In addition, the surface roughness of Fe-Si film with a thin Ru underlayer became smaller than that without an Ru underlayer. Consequently, the hard axis coercivity of the Fe-Si film with a 1 nm Ru underlayer was about 1.1 Oe, which was much lower than that of the same film without an Ru underlayer. The Fe-Si film with a 1 nm Ru underlayer had a clear uniaxial magnetic anisotropy (anisotropy field Hk: 18 Oe), a hard axis relative permeability of 900, and a ferromagnetic resonance (FMR) at around 1.6 GHz. A very sharp peak of the imaginary part of permeability μh" was observed at the FMR frequency. This was due to the clear uniaxial magnetic anisotropy and small anisotropy dispersion.

Interface structure and stabilization of metastable B2-FeSi/Si(111) studied withlow-energy electron diffraction and density functional theory

We present a combined experimental and theoretical investigation of the interfacebetween a B2-type FeSi film and Si(111). Using an ultra-thin B2-FeSi film grownon Si(111), the interface is still reached by electrons, so quantitative low-energyelectron diffraction (LEED) could be applied to determine the bonding geometryexperimentally. As a result, the local configuration at the shallow buriedinterface is characterized by near-substrate Fe atoms being 8-fold coordinatedto Si atoms and by the silicide unit cell being rotated by 180° withrespect to the Si unit cell (B8 configuration). The interface energetics wereexplored by total-energy calculations using density functional theory (DFT). TheB8-type interface proves to be the most stable one, consistent with theexperimental findings. The atomic geometries obtained experimentally (LEED)and theoretically (DFT) agree within the limits of errors. Additionally, thecalculations explain the stabilization of the B2 phase, which is unstable as bulkmaterial: the analysis of the elastic behaviour reveals a reversed energy hierarchyof B2 and the bulk stable B20 phase when epitaxial growth on Si(111) is enforced.

Ｆｅ‐Ｓｉ（１１１）合金単結晶膜の作製と磁気特性

(111) oriented single-crystal films of Fe-Si alloy were prepared on Si(111) substrates by dc facing-targets sputtering. Excellent crystalline quality was obtained for film thicknesses from 100 nm to 1.0μm. Soft magnetic property was achieved for a 100 nm-thick Fe-Si(111) film sputtered by using Fe-10%Si targets. In-plane uniaxial magnetic anisotropy was observed in magnetization curves and permeability of a Fe-Si(111) film prepared by using Fe-12%Si targets, with the hard-axis parallel to the magnetic field between two targets (the oblique angle of incidence). Structural asymmetry was not observed in X-ray diffraction measurements. However, the temperature dependence of the anisotropy field shows that the directional order of Fe and Si atoms is not related to the origin of uniaxial anisotropy.

Single-Pole Heads with Thin Fe-Si Main-Pole Films

The linear recording density in perpendicular magnetic recording is limited by the thickness of the main-pole in the single-pole head. In order to raise the practical readback resolution, a thin main-pole film is indispensable. Fe-Si film has a large saturation magnetization and good soft magnetic properties are obtained at thicknesses between 50 and 200 nm. However, as the film thickness decreases below 100 nm, the domain wall structure and domain configuration change from Bloch-type walls and closure domains. A head with such a thin film as its main-pole has unstable readback output and poor resolution. The authors therefore adopted as the main-pole an Fe-Si/SiO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> multi-layered film whose domain structure differs from that of a single-layer Fe-Si film. As a result, the output stability and high-density response could be improved by controlling the intermediate layer (hereafter "inter-layer") thickness and the number of magnetic layers.

Formation of ironsilicide on Si(001)

Ultrathin epitaxial films of β-FeSi 2 were grown on Si(001) by room temperature (RT) deposition of Fe followed by annealing. During the various stages of the growth process the lattice structure, composition and morphology of the films were investigated by medium-energy ion scattering in conjunction with shadowing and blocking. At RT the deposited Fe reacts with the Si(001) substrate and forms a continuous film of average composition FeSi, or Fe 5Si 3, depending on the deposited amount of Fe. After annealing the FeSi film to 670 K, a conversion into β-FeSi 2 has taken place and the film is no longer continuous. The β-FeSi 2 films grown are composites of two azimuthal orientations with respect to the substrate: the predominant A orientation with β-FeSi 2 [010]⋎Si〈110〉 and the B orientation with β-FeSi 2 [010]⋎Si〈100〉.