Wear-resistant magnetic thin film material based on aTi1−xFexC1−ynanoc

Abstract

In this study we report on the film growth and characterization of thin ͑approximately 50-nm-thick͒ Ti-Fe-C films deposited on amorphous quartz. The experimental studies have been complemented by first-principles density-functional theory ͑DFT͒ calculations. Upon annealing of as-prepared films, the composition of the metastable Ti-Fe-C film changes. With increasing annealing time, there is a depletion of iron close to the surface of the film, while regions enriched in iron are simultaneously formed deeper into the film. Both the magnetic ordering temperature and the saturation magnetization changes significantly upon annealing. The DFT calculations show that the critical temperature and the magnetic moment both increase with increasing Fe and C-vacancy concentration. The formation of the metastable iron-rich Ti-Fe-C compound is reflected in the strong increase in the magnetic ordering temperature. Eventually, after enough annealing time ͑Ն10 min͒, nanocrystalline ␣-Fe starts to precipitate, the amount and size of which can be controlled by the annealing procedure; after 20 min of annealing, the experimental results indicate a nanocrystalline iron-film embedded in a wear-resistant TiC compound. This conclusion is further supported by transmission electron microscopy studies on epitaxial Ti-Fe-C films deposited on single-crystalline MgO substrates where, upon annealing, an iron film embedded in TiC is formed. Our results suggest that annealing of metastable Ti-Fe-C films can be used as an efficient way of creating a wear-resistant magnetic thin film material.

Carbide and nanocomposite thin films in the Ti–Pt–C system

“…The only change in the C1s peak (not shown) upon annealing is the disappearance of the C-Pt bonds. [18]. These different behaviours can be understood from the theoretical results of Hugosson et al, who shows that the surface segregation energy of the group 11 metals in TiC are considerably lower than for the other transition metals [28].…”

“…Comparing with previous studies on the Ti-Fe-C and Ti-Ni-C systems [15][16][17][18], these temperatures should be sufficient for the metastable solid solution to decompose and crystallise the weak carbide forming metal.…”

“…The weak carbide former substitutes some of the Ti, forming (Ti 1-x Me x )C. This has, e.g., been shown for the Ti-Fe-C, Ti-Ni-C, and Ti-Cu-C systems [15][16][17]. It has also been shown that these metastable solid solutions can decompose by forming a separate metal phase of the weak carbide former [15][16][17][18]. It should hence be possible to produce the desired ncTiC x /a-C/nc-Pt structure, either during codeposition of the elements, or by codeposition followed by post-deposition annealing of metastable (Ti 1-x Pt x )C thin film.…”

Carbon release by selective alloying of transition metal carbides

“…The sub-stoichiometric phases on the other hand, while having a lower number of unfavorable metal-carbon bonds in the system, are also stabilized due to an increased metal-metal bonding in these phases. This change in behavior of the bonding has also been shown to be reflected in the magnetic exchange interactions between Fe atoms in ternary Ti-Fe-C. [29] We now turn our attention to the possibility of C to leave the system in the form of graphite as a response to the alloying with the metal M. The relevant property to consider from the theory is in this case the energy difference, ∆E, which is illustrated in Fig. 1.…”

Control of crystallinity in sputtered Cr–Ti–C films

“…The properties of these nanocomposites are typically affected by the relative amount of a hard carbide phase in a softer a-C matrix [4][5][6][7]. For the 3d transition metals, the tendency to form amorphous films increases with increasing number of d-electrons in the metal and sputtered Cr-C and Fe-C films are therefore often amorphous [8][9][10][11]. This trend has been explained based on factors such as differences in atomic radii, carbide stability, and carbide crystal structure (see, e.g., ref.…”