Crystal structure and local ordering in epitaxial Fe100−Ga /MgO(001) films

Abstract

In this work we present a study of the structural properties of Fe 100−x Ga x (x<30) films grown by Molecular Beam Epitaxy on Mg0(100). We combine long range and local/chemically selective X-ray probes (X-ray Diffraction and X-ray absorption spectroscopy) together with real space imaging by means of Transmission Electron Microscopy and surface sensitive in situ Reflected High Energy Electron Diffraction. For substrate temperature T s below 400 o C we obtain bcc films while, for x ≈ 24 and T s ≥ 400 o C the nucleation of the fcc phase is observed. For both systems a Ga anticlustering or local range ordering phenomenon appears. The Ga/Fe composition in the first and second coordination shells of the bcc films is different from that expected for a random Ga distribution and is close to a D0 3 phase, leading to a minimization of the number Ga-Ga pairs. On the other side, a long-range D0 3 phase is not observed indicating that atomic ordering only occurs at a local scale. Overall, the epitaxial growth procedure presented in this work, first, avoids the formation of a long range ordered D0 3 phase, which is known to be detrimental for magnetostrictive properties, and second, demonstrates the possibility of growing fcc films at temperatures much lower than those required to obtain bulk fcc samples.

Magnetic ripple domain structure in FeGa/MgO thin films

“…The samples are referred in the text with two of numbers describing composition and thickness, thus 13-17 stands for the film with Ga content 13 % and t f = 17 nm. Figure 1 shows atomic force microscopy images on films grown at T s = 150 o C and T s = 600 o C with bcc crystal structure [17]. The image of the films grown at T s = 150 o C, obtained from sample 24-20, is representative of the topography of the films studied by MFM.…”

“…Magnetic force microscopy images presented in Fig 2a) shows lines on the film surface, interpreted as magnetic domain walls, separating areas without contrast, indicating that M is confined in the plane, and also some tip induced features; the image displayed in Fig 2b, taken for film 24-20, shows a fine structure which is not observed in the areas separated by the domains walls of the image 2a for film [13][14][15][16][17]. Fig 2c and 2d shows the same kind of magnetic contrast, revealing a non uniform magnetic configuration, in more detail for films with 28-56 and 28-21, respectively.…”

“…For Q < 1, the film thickness has to be larger than the critical value to develop a stripe structure [27]. Figure 3b For the films presented, the ME contribution does not induce perpendicular anisotropy because the signs of the film strains [17] and the B 1 ME coefficient result in a contribution that favors the in-plane orientation of M. The contribution due to an asymmetric distribution of the NNN Ga-Ga pairs proposed to explain the anisotropies in other Fe-Ga films could also explain the presence of a positive K u [8]. The simplest estimation of K u can be done by assuming that the total in-plane anisotropies correspond to 0.5µ 0 M 2 s .…”

Local and Medium Range Order Influence on the Magnetic Behavior of Sputtered Ga-Rich FeGa Thin Films

“…19 To study the local range order, the use of X-ray absorption fine structure (XAFS) measurements are crucial since they can provide information about the electronic structure and local geometry of the scattering atom when using x-ray absorption near edge structure (XANES), and about the degree of disorder by means of extended x-ray absorption fine structure (EXAFS). 9,[19][20][21][22] In the sputtering process, neutrals (atoms ejected from the target upon the impact of energetic particles) suffer collisions on their movement from the target to the substrate. [23][24][25] If the number of collisions is low, neutrals keep their momentum and energy till the substrate, and the sputtering growth takes place under ballistic flow.…”

From Waste to Multi-Hybrid Layering of High Carbon Steel to Improve Corrosion Resistance: An In-Depth Analysis Using EPMA and AFM Techniques

“…The selective diffusion layer formed a composite characteristic between E values of alumina and steel, whereas on the main steel substrate, it remained unchanged for approximately 200.0 GPa, in agreement with the typical Young's modulus ranges of steel. The increased Young's modulus value of this compared to the steel substrate was attributed to the presence of the dominant Fe-Mg-O combination that had good corrosion resistance and mechanical hardness nature [24,25], considering this layer was fabricated with the carbide layer (C, Ca, Cr, and Si elements). A similar behaviour on the Mn-based selective diffusion layer offered higher hardness.…”