The Effect of deposition rate on FePt/MgO crystal orientation

Highlights: • Deposition rate of these nanoparticles has effect on crystal orientation of them on polycrystalline MgO layer. • At rates higher than 1.5 Å/s (001) direction and at rates lower than 1 Å/s (111) directions are preferable. • At medium deposition rates, different crystal directions of FePt nanoparticles are appeared in XRD analyses. • In high deposition rate the probability of transmission from an energy barrier decreases. - Abstract: FePt granular layers which are made in suitable conditions can have three types of ordering that are crystalline, compositional orders and directional configuration of nanoparticles. Formation of fct structure with L1₀ compositional ordering requires high temperature. At this temperature, a problem is the size control of the nanoparticles and another problem is control of their crystal orientation. Fabrication method and the use of suitable substrates can help solving these problems. In direct synthesis by sputtering method on the warm substrate the size of FePt nanoparticles in L1₀ compositional ordered phase can be controlled. We show that crystal orientation of L1₀-FePt nanoparticles on a thin layer of MgO depends on the rate of deposition. This becomes clear from the results of the XRD analyses of samples. Based on these results in synthesis at room temperature with deposition rate of upper than 1.5 Å/s after annealing, (001) peak is dominated and at rate of lower than 1.0 Å/s just (111) peak is appeared. In direct synthesis with intermediate rate (111) and (110) peaks can be seen. Moreover, the difference of the shape of hysteresis loops of samples in parallel and vertical directions are the witnesses for orientation of samples in presence of MgO layer and the effect of FePt deposition rate on it.