Grain growth in ultrathin films of CoPt and FePt

Abstract

The microstructure of sputtered 10-nm thin films of equiatomic binary alloys of CoPt and FePt was characterized using transmission electron microscopy (TEM). Grain growth kinetics was examined using manual and digital analysis of bright-field TEM images and was seen to take two stages during annealing in these films. A rapid growth stage concurrent with the formation of a [111] fiber texture was observed to occur within the first 5-10 min of annealing, followed by a much slower growth stage after the fiber texturing was well advanced. Differences in grain growth rate and ultimate grain size were also observed to depend on heating rate.

Thermal annealing of FePt thin films by millisecond plasma arc pulses

“…Though Buschbeck et al [13] have explored laser annealing, the pulse width was in the nanosecond regime, which is orders of magnitude too fast to allow for sufficient atomic diffusion. Others have reported conventional rapid thermal annealing techniques [14][15][16][17], but these time scales are in seconds to tens of seconds, which are orders of magnitude too long. This paper reports the use of a plasma arc lamp that is capable of thermally annealing materials with pulse widths as short as tens of milliseconds over several square centimeters simultaneously [18][19][20].…”

Thickness dependence of the phase transformation in FePt alloy thin films

“…Then the randomly oriented grains are consumed until each grain has mostly [1 1 1] oriented neighbors leading to decrease of the interface energy due to coherence between matrix and product phase. Thus, the ordering process is triggered and proceeded as a result of the grain coalescence in the films [4,13].…”

Ta clustering and microstructural evolution in the A1 to L1Fe52PtX(Ta1−X) phase transformation

“…For fcc-based structures, which is the A1 symmetry, the ͑111͒ closed packed planes are the lowest free energy surface. 4 The formation of this surface competes with the lowest strain energy fiber direction ͓001͔. 4 The addition of the Ta, even for low concentration of 1.4 at.…”

“…4 The formation of this surface competes with the lowest strain energy fiber direction ͓001͔. 4 The addition of the Ta, even for low concentration of 1.4 at. %, allowed the strain energy to dominate the fiber growth of the film.…”

“…2,3 Unfortunately, this annealing results in grain coarsening and the loss of the narrow grain size distribution required for small bit sizes in magnetic storage applications. 3,4 There is significant research interest in ternary alloying additions which can either lower the ordering temperature and/or reduce the extent of grain growth through pinning the grain boundaries. 5,6 For example, minor additions of Cu have been shown to reduce the ordering temperature by approximately 200°C but, unfortunately, facilitated grain growth.…”