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

Abstract

FePd thin films have been recently considered as promising materials 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)]5 multilayers were thermally evaporated in an ultrahigh vacuum on MgO(100), Si(100), Si(111), and Si(100) covered by a 100-nm-thick layer of amorphous SiO2. In order to obtain a homogeneous FePd:Cu alloy, the multilayers were annealed in two different ways. First, the samples were rapidly annealed in nitrogen atmosphere at 600 °C for 90 seconds. Next, the long annealing in a high vacuum for 1 h at 700 °C 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 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 the texture category is substrate-dependent.