Chemical order and crystallographic texture of FePd:Cu thin alloy films

Abstract

FePd thin films have been recently considered as promising material for high-density magnetic storage devices. However, it is necessary to find a proper method of fabrication for the (001)-textured and chemically well-ordered alloy. In this paper, we present the detailed investigations of lattice parameters, chemical order degree, grain sizes and crystallographic texture, carried out on FePd alloys with 10 at.% of Cu addition. The initial [Cu(0.2 nm)/Fe(0.9 nm)/Pd(1.1 nm)]x5 multilayers were thermally evaporated in an ultra-high vacuum on MgO(100), Si(100), Si(111) and Si(100) covered by 100 nm thick layer of amorphous SiO2. In order to obtain homogeneous FePd:Cu alloy, the multilayers were annealed in two different ways. First, the samples were rapidly annealed in nitrogen atmosphere at 600oC for 90 seconds. Next, the long annealing in a high vacuum for 1 hour at 700oC was done. This paper focuses on quantitative investigations of the chemical order degree and crystallographic texture of ternary FePd:Cu alloys deposited on four different substrates. In order to obtain both quantities we have taken a novel approach to consider the problem of dopant atoms located in the FePd structure. The studies of the structure were done using X-Ray Diffraction (XRD) performed with synchrotron radiation and pole figures measurements. We have found that the addition of Cu changes the FePd lattice parameters and lattice distortion. We have also shown, that using different substrates it is possible to obtain a FePd:Cu alloy with different chemical order and texture. Moreover, it was observed that texture category is substrate dependent

Determination of grain shape of laser-irradiated FePdCu thin alloy films

“…[12] The same authors reported, that for well-ordered FePd alloys Cu admixture causes decrease of c value with simultaneous increase of a value, in comparison to the bulk values.…”

“…Our previous studies showed, that FePdCu thin alloy films on Si(100) substrate revealed the fiber texture of [111] and [001] crystallites. [12] It manifested in the cylindrical symmetry of grains oriented around the axis normal to film plane. Therefore, the result of ω-scan did not depend on the polar angle at which the sample was placed with respect to the incident X-ray beam.…”

“…It is worth mentioning, that the model does not take into account the temperature dependencies of the material properties such as absorption, density, specific heat and thermal conductivity, and assumes, that between laser pulses they do not change. The peak temperature of 500 circ C was chosen basing on results of our previous investigations, [9,11,12] which showed that it is the minimum temperature required to induce a diffusion process, and to start transformation from multilayer system into ordered alloy.…”

“…To reduce the temperature of L1 0 structure formation and to induce (001) texture the FePd alloy was doped with Cu, as it was observed in our previous studies. [11,12] We present here the studies of the laser annealing effect on the structure, surface morphology, grain size and shape of FePdCu thin alloy films.…”

Magnetic anisotropy axis reorientation at ultrathin FePt films

“…For calculating the chemical ordering parameter S of the films, the intensity of the (001) and (002) peaks is measured. S may be calculated by the following formula : where I 001 and I 002 are the integrated intensities of the corresponding XRD peaks, calculated from least‐squares pseudo‐Voigt fitting . The deconvolution of the mixed (200) and (002) peak yields the integrated area of the L1 0 (002) peak (for more details see Supporting Information).…”