Magnetic Properties of Percolated Perpendicular FePt–MgO Films

Abstract

Percolated perpendicular FePt-MgO films with a (Fe 48 Pt 52 ) 100 -(MgO) /Pt(001)/Cr(002) structure were prepared by conventional dc magnetron sputtering (x = 0 6 13). Magnetic measurements demonstrate that the coercivity of the magnetic film drastically increases from 169 to 285 kA/m as the MgO content is increased from 0 to 0.15 vol.%. However, the grain sizes of the FePt phase do not significantly varying upon doping with MgO. MgO does not appear at the grain boundaries of the FePt phase, but is present as crystalline dots that are uniformly precipitated in the FePt matrix. The MFM images revealed that the domain structure transformed from extending to isolate when the MgO dots precipitated into the FePt grains. Consequently, the MgO dots serve as pinning sites of the domain wall and enhance perpendicular coercivity. Percolated perpendicular magnetic recording is thus regarded as a solution to the problem of thermal instability in ultrasmall grains.

Comparative evaluation of performance of percolated perpendicular media using FePt–MgO/Pt/Cr trilayer and FePt–MgO/MgO bilayer

“…The XRD data for the Pt underlayered FePt-MgO films with various MgO contents show that the initial incorporation of MgO does not alter the crystalline structure [16] until the amount of MgO exceeds 0.15 vol%. A transformation of lattice orientation was observed at xX0.15.…”

Development of high density magnetic recording media for hard disk drives: materials science issues and challenges

“…Choice of any other temperature range and time duration or of a higher SiO 2 volume will lead to poor magnetic properties. However, the work by Sun et al 127 showed that the precipitation of MgO nanodots in the FePt matrix contributes to an increased the medium coercivity, which is quite different from the statement by Laughlin et al 125,126 that only the oxide nanopillars are effective for pinning. Consequently, more work should be conducted in the near future to understand the 13 Sketches of a traditional granular perpendicular media and b percolated perpendicular media: the transition parameter mainly depends on the grain size and exchanging coupling in a, while it mainly depends on the density, size and regular distribution of the pinning sites in b, where the white spots represent the pinning nanophase pinning effects, e.g.…”

“…22 and above, several proposals have been addressed so far to try to solve the 'trilemma' problems. These include percolated perpendicular media, [121][122][123][124][125][126][127][128] bit patterned media, heat assisted media, [153][154][155][156][157][158][159][160][161][162][163][164] continuous granular composite media (CGC) [165][166][167][168][169] and exchange spring media. [170][171][172][173][174][175] Since last two kinds of media (CGC media and exchange spring media) have been well documented in the literature, [165][166][167][168][169][170][171][172][173][174][175] we focus our attention in this section only on the first three cases, in particular, with respect to their principles of magnetism, media development from a viewpoint of materials science, engineering progress so far and directions in the near future.…”

Overcoming the Trilemma Issues of Ultrahigh Density Perpendicular Magnetic Recording Media by L10-Fe(Co)Pt Materials

“…Moreover, Sun et al prepared the percolated perpendicular FePt-MgO¯lms by conventional magnetron sputtering. 68 Magnetic measurements demonstrate that the coercivity of the magnetic¯lm drastically increases from 2.1 to 3.6 kOe as the MgO content is increased from 0 vol. % to 0.15 vol.%.…”

“…65,67 Figure 13 shows the TEM images of CoPt-SiO 2 and (FePt)-(MgO)/ Pt/Cr thin¯lms. 67,68 The plan-view image of asdeposited CoPt-SiO 2¯l m [ Fig. 13(a)] has a microstructure similar to conventional GPM.…”