Abstract
BN is the currently required segregant for perpendicular FePt media. We found that BN can be diffused from the MgTiOBN intermediate layer during a high temperature process. The FePtCAg film sputtered on MgTiOBN layers illustrates higher perpendicular magnetocrystalline anisotropy (Ku) (1.43 × 107 erg/cm3) and coercivity (normal to film surface) (17 kOe) at 350 K compared to BN/FePtCAg/MgTiON film. From the microstructure, the FePtCAg film shows the granular structure on the MgTiOBN intermediate layer, but parts of the irregular FePt grains are agglomerated and partially separated in the matrix, with grains size being, on average, 26.7 nm. Cross-sectional imaging showed that the FePt grains have a truncated pyramid shape with a lower wetting angle, which is influenced by the surface energy of MgTiOBN. BN segregation at FePt grains or boundaries is still not clear. Using the electron energy loss spectrum (EELS), we found that part of the BN atoms were clearly observed in the FePt lattice and iron-boride oxide was indexed in the x-ray photoelectron spectroscopy (XPS) spectra. To determine the effects of BN segregant (from capping layer or intermediate layer) on the magnetic switching behavior of FePtCAg film, the intrinsic-(ΔHint = 6.17 kOe, 6.54 kOe) and extrinsic- (ΔHext = 0.80 kOe, 0.39 kOe) switching field distribution (SFD) were measured by plotting saturated major- and unsaturated minor- hysteresis loops to evaluate the crystal orientation and microstructure (grains volume and distribution) for BN/FePtCAg/MgTiON and FePtCAg/MgTiOBN films, respectively. The main contribution of intrinsic SFD is the c-axis misalignment for the BN/FePt/MgTiON sample; however, the dispersed magnetic anisotropy has a higher input to intrinsic SFD for FePtCAg/MgTiOBN/CrRu film.
Highlights
Energy-assisted magnetic recording (MR), for example, heat-assisted MR, is a new technology that boosts hard disk area density beyond 2 Tb/in2
To extend the superparamagnetic effect of CoCrPt-(oxides) in perpendicular MR, higher magnetocrystalline anisotropy (Ku ) material, L10 FePt film is optimal in this system [1–4]
The FePtCAg/MgTiOBN and BN/FePtCAg/MgTiON samples were deposited by magnetron sputtering on the CrRu seed layer, which were sputtered on a glass substrate (Corning, Eagle XG, Taipei, Taiwan)
Summary
Energy-assisted magnetic recording (MR), for example, heat-assisted MR, is a new technology that boosts hard disk area density beyond 2 Tb/in. The hard disk drive (HDD) based on FePt media has recently been tested in selected customers [5–8]. The intermediate layer has suitable lattice mismatch and provides a template for the growth of c-axis or (001) textured FePt film. The MgO-related materials, for example, using transition metal ion or nitride such as (Ti, Cu, Co, Ni, TiN) to replace part of the Mg2+ to improve the MgO target conductivity, have been discussed [9–12]. The surface energy and lattice misfit strain can be tuned between FePt and the intermediate layer and, the FePt (00L) film can be sputtered on a (002) textured MgO-based intermediate layer using direct current magnetron sputtering
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