Nanocomposite CoPt:C films for extremely high-density recording

Abstract

Nanocomposite CoPt:C films were investigated as potential media for extremely high-density recording. An annealing temperature of over 600 °C is necessary to form nanocomposite CoPt:C films consisting of C matrix and fct CoPt nanocrystallites with grain sizes of 8–20 nm and coercivities of 3–12 kOe. Coercivity and grain size increase with increasing annealing temperature and decreasing C concentration and they are insensitive to film thickness. The average activation volumes are about 0.9×10−18 cm3. The properties of these nanocomposite CoPt:C films can be tailored to satisfy the thermal stability, coercivity, and media noise requirements for extremely high-density recording.

Unconventional magnetic behavior of iron-oxide nanoparticles in polymeric matrices

“…6͑a͔͒; ͑ii͒ the sample was exposed to a field gradient of low intensity ͑0.4 kOe͒, where the angle between the magnetic field and the sample changed from 45°to 135°; ͑iii͒ spectrum recorded on sample exposed to a field of 0. 4 kOe applied perpendicular to the ␥ beam ͓Fig. 6͑b͔͒; and ͑iv͒ zero field spectrum recorded after removing the field ͓Fig.…”

“…Examples of current interest include magnetically hard and soft metallic alloys, 1 core-surface nanoparticles, 2 and nanocomposite films. 3,4 Recently, a new magnetic behavior has been observed at low temperature ͑5 K͒ in insulating composites based on crystalline ␥-Fe 2 O 3 ͑maghemite͒ nanoparticles dispersed in a solid polymer matrix, 5 prepared by freezing a methanol based ferrofluid of the composite: magnetic particles have been observed rotating freely in response to an applied static magnetic field ͑i.e., ''free rotor behavior''͒ after conditioning the material in a cycling magnetic field.…”

Effects of rapid thermal annealing on nanostructure, texture and magnetic properties of granular FePt:Ag films for perpendicular recording (invited)

“…One way to solve this problem is to use nanocomposite films, in which the grain growth can be suppressed by nonmagnetic matrix. 6,7 For example, the studies of CoPt:C, 8,9 FePt:B 2 O 3 , 10,11 and CoPt:B 2 O 3 12 films have been reported. In this study, rapid thermal annealing processing conditions and the nanostructural and magnetic properties of FePt:Ag films are presented.…”

Orientation-controlled nonepitaxial L1 CoPt and FePt films

“…By controlling the thickness, composition, and annealing conditions, and/or depositing a proper underlayer, nearly perfect ͑001͒-oriented CoPt and FePt films can be obtained. Recently, L1 0 structured CoPt and FePt films, [1][2][3][4] CoPt and FePt based nanocomposite films 5,6 and FePt selfassembled nanoparticles 7 have attracted much attention. These high anisotropy materials show great potential for high-density magnetic recording because of their ability to achieve extremely small grain sizes.…”