HITPERM/SiO 2 single and multilayer thin films have been produced using a target composition of (Fe70Co30)88Zr7B4Cu1. The as-deposited HITPERM film contains small bcc (or B2) nanocrystals of volume fraction less than 10% surrounded by an amorphous matrix. The lattice parameter of the nanocrystal is about 5% larger than an equilibrium FeCo phase. The saturation induction determined from FMR measurements (1.53±0.08 T) is consistent with VSM and SQUID measurements (1.45–1.5 T) and also with as-spun amorphous ribbons (1.55–1.62 T). The Landé g-factors (2.15±0.05) are typical of transition metals, particularly, of Fe. The Landau–Lifshitz–Gilbert damping parameters of the single and multilayered films are small (α = 0.0055±0.0004) with each layer acting almost independently. Neither thickness variation of each layer nor the number of stacking significantly affects the damping process in a range of film thicknesses of 50–150 nm, while the coercivities are strongly dependent on those parameters. This supports a notion that the damping parameter is an intrinsic property.

We describe the effects of TixZr1-x underlayers on the microstructural and magnetic properties of CoCrPtB layers. We found that as the Zr atomic composition increases in the TixZr1-x underlayers, the unit cells of the TixZr1-x underlayers expand. The TixZr1-x (0002) texture is strongest as the Zr atomic composition ranges from 40% to 60%. In addition, the CoCrPtB (10002) texture induced by the (0002) textured TixZr1-x underlayer is enhanced at these optimizing Zr compositions. The grain size of the CoCrPtB layers deposited onto the TixZr1-x underlayers is around 7.5-9.5 nm. Stacking fault streaks observed by transmission electron microscopy indicate that stacking faults exist in the CoCrPtB films with the TixZr1-x underlayers. The Hc (coercivity) and S* (squareness) of the CoCrPtB magnetic layers deposited onto the pure Ti and Zr underlayer were higher than those with the TiZr alloy underlayers.

We describe a new Ni5Al3 underlayer for high-density longitudinal magnetic recording. The Ni5Al3 underlayer has the FCC derivative Ga3Pt5 structure. The Ni5Al3 (221) plane has good lattice match with the CoCrPt (10 (1) over bar0) plane. In addition, unlike the NiAl (112) plane, the Ni5Al3 (221) plane has the lowest surface energy. Hence, the Ni5Al3 thin film has a strong (221) texture and can induce CoCrPt (10 (1) over bar0) texture. The microstructure and magnetic properties of the CoCrPt-Ni5Al3 thin films are reported and discussed.

Amorphous precursors to HITPERM (Fe, Co)-Zr-B-Cu (a-HITPERM) films and a-HITPERM/SiO2 multilayer films have been deposited on glass or Si substrates by a rf sputtering system with a target of composition (Fe0.7Co0.3)(88)Zr7B4Cu1. It was found that the a-HITPERM single layer film with a thickness of 100 nm possessed good soft magnetic properties with a saturation magnetization of 4 piM(s) greater than or equal to 14 kG and a coercivity of H-c similar to 0.9 Oe at room temperature. He increases from 0.9 Oe to 25 Oe when the film thickness increases from 100 to 150 nm. To obtain excellent soft magnetic properties at larger thicknesses, a-HITPERM/SiO2 multilayer films have been synthesized. In these, H-c drops from 25 Oe (single layer) to 0.25 Oe (multilayers) with the same total a-HITPERM thickness. The intervening SiO2 layers play an important role in reducing the coercivity. Experimental results show the optimum thickness for SiO2 was 2-4 nm. M-H loops for the multilayers films exhibit pronounced two step magnetization reversal processes for temperatures between 5 and 25 K. This behavior can be attributed to magneto-static coupling between a-HITPERM layers and sequential switching of the layers. The coupling exhibits itself in a blocked phenomenon with wide (stepped) hysteresis curves for T < 25 K and smooth narrow hysteresis curves for T > 25 K. The effects of magneto-static coupling on the magnetic properties of a-HITPERM/SiO2 films will be discussed.

40 nm thick CoPt and FePt films were prepared on oxidized Si substrates with 10 nm MgO underlayers. The maximum coercivity (H/sub c/) for CoPt films was found to be /spl sim/10 kOe after annealing at 700/spl deg/C for /spl sim/20-30 minutes (min). Structural analysis showed a significant amount of FCC phase as well as the ordered L1/sub 0/ phase in these films. FePt films showed an abrupt increase of ordered volume fraction and H/sub c/ in the initial stage of annealing and predominance of the tetragonal L1/sub 0/ phase after 10 min. at 700/spl deg/C. The maximum H/sub c/ reached /spl sim/16 kOe after annealing at 700/spl deg/C for more than 20 minutes. Dark field (DF) images of the annealed CoPt films showed individual grains which exhibited a possibility of several variants or disordered phase with dimensions similar to the exchange correlation length, b/sub cm/. The temperature dependence of H/sub c/ seems to indicate a weak pinning mechanism in the highly ordered FePt films. Magnetic force microscopy indicated a complex domain structure consisting of clusters with dimensions of several hundred nanometers.

In this work Ag underlayers, with a slightly larger unit cell than FePt, were found not only to induce epitaxial growth of the FePt films but also to reduce the FePt ordering temperature. Without using the Ag underlayer, the FePt film deposited onto the Si substrate was fcc disordered. By the use of the Ag underlayer, it was observed that the FePt unit cells were expanded in the film plane. This has caused the shrinkage of the FePt unit cells along the film normal direction and resulted in the in situ ordering of the FePt thin film at reduced temperatures. The microstructural and magnetic properties of the FePt/Ag films at varied substrate temperature and FePt thickness were studied to investigate the L10 FePt ordering.

Disordered fcc (face-centered-cubic) [100] fiber-textured CoPt thin films with thicknesses of 20-40 nm were deposited on a nonmagnetic sputtered MgO seed layer with and without a Ag intermediate layer. These were subsequently annealed at 600-750 degrees C for 5-10 min using rapid thermal annealing (RTA). The structural variants were determined to coexist in the in-plane and normal to the plane directions after the RTA process. The MgO underlayer without the intermediate layer revealed strong in-plane anisotropy by magnetic hysteresis measurement. Selected area diffraction (SAD) by TEM and XRD measurements for these samples confirmed the preferential growth of in-plane variants of c axis compared to the perpendicular direction. High remanence and coercive squareness (S*) were obtained due to strong in-plane texture and especially due to exchange coupling among the grains. Evidence for this was provided by Delta M curves. Initial magnetization curves for samples annealed above 600 degrees C, showed the possibility of assembled single domain or domain pinning mechanism but with negligible free wall motion inside of the grains. (C) 2000 American Institute of Physics. [S0021-8979(00)61008-3].

Mn3Si possesses a D0(3) structure, which is a bcc derivative structure with nearly the same atomic spacing as Cr and NiAl which have been commonly used for longitudinal magnetic recording underlayers. AG(30 nm)/CoCrTa(40 nm)/Mn3Si(x, x=100, 200, 400 nm)/Ag(75 nm) thin films were sputter deposited onto hydrofluoric acid (HF)-etched Si:(001) substrates at elevated temperature. Compared to the 100 and 200 nm thick Mn3Si samples, the XRD spectrum of the 400 nm thick Mn3Si sample shows a significant increase in the intensity of the Mn3Si(002) peak. This suggests that a high volume fraction of the D0(3) phase was formed. The CoCrTa(11 (2) over bar 0) peak intensity has been found to increase with Mn3Si thickness. As a result, the in-plane coercivity increases as the volume fraction of the D0(3) phase increases. (C) 2000 American Institute of Physics. [S0021-8979(00)88408-X].

Polycrystalline MgO underlayer films lead to different preferred orientations of L1/sub 0/ CoPt and FePt films after the annealing process, depending on the thickness of the L1/sub 0/ films. L1/sub 0/ films with a thickness greater than 20 nm revealed mostly L1/sub 0/ [100] fiber texture and consequently in-plane anisotropy as determined by magnetic hysteresis. Strong perpendicular anisotropy due to the L1/sub 0/ [001] fiber texture was obtained for thicknesses below 10 nm. The /spl delta/M curve showed strong intergranular exchange coupling. The angular variation of coercivity showed the possibility of both domain wall motion and a rotational mechanism of magnetization reversal.

Mn3Si possesses a D0 3 structure, which is a bcc derivative structure with nearly the same atomic spacing as Cr and NiAl which have been commonly used for longitudinal magnetic recording underlayers. AG~30 nm!/CoCrTa~40 nm!/Mn3Si(x, x5100, 200, 400 nm)/Ag ~75 nm! thin films were sputter deposited onto hydrofluoric acid ~HF!-etched Si: ~001! substrates at elevated temperature. Compared to the 100 and 200 nm thick Mn 3Si samples, the XRD spectrum of the 400 nm thick Mn3Si sample shows a significant increase in the intensity of the Mn 3Si~002! peak. This suggests that a high volume fraction of the D0 3 phase was formed. The CoCrTa ~112̄0! peak intensity has been found to increase with Mn 3Si thickness. As a result, the in-plane coercivity increases as the volume fraction of the D0 3 phase increases. ©2000 American Institute of Physics. @S0021-8979 ~00!88408-X#

Disordered fcc (face-centered-cubic) [100] fiber-textured CoPt thin films with thicknesses of 20–40 nm were deposited on a nonmagnetic sputtered MgO seed layer with and without a Ag intermediate layer. These were subsequently annealed at 600–750 °C for 5–10 min using rapid thermal annealing (RTA). The structural variants were determined to coexist in the in-plane and normal to the plane directions after the RTA process. The MgO underlayer without the intermediate layer revealed strong in-plane anisotropy by magnetic hysteresis measurement. Selected area diffraction (SAD) by TEM and XRD measurements for these samples confirmed the preferential growth of in-plane variants of c axis compared to the perpendicular direction. High remanence and coercive squareness (S*) were obtained due to strong in-plane texture and especially due to exchange coupling among the grains. Evidence for this was provided by ΔM curves. Initial magnetization curves for samples annealed above 600 °C, showed the possibility of assembled single domain or domain pinning mechanism but with negligible free wall motion inside of the grains.

Various aspects of the structure of thin film longitudinal recording media are presented and discussed. In particular we discuss the role that the various layers of thin film media play in controlling the microstructure and magnetic properties of the magnetic layer. These include the grain size of the films, the texture of the films, the role of the intermediate layer and the role of chemical segregation.

In situ ordering of FePt thin films by sputtering onto Ag/Si and Ag/Mn3Si/Ag/Si templates has been demonstrated. Due to the evolution from island-like to a continuous film structure as a function of Ag thickness, the ordering and orientation of the FePt films both change with Ag thickness. A continuous (002) Ag film results in a greater L1(o) phase formation with c-axis oriented both perpendicular to and in the film plane while the island-like Ag template results in less L1(o) phase formation, hut a preferential c-axis orientation in the film plane. On the other hand, the FePt films deposited onto the Ag/Mn3Si/Ag/Si template have their c axes aligned perpendicular to the film plane.

In situ ordering of FePt thin films by sputtering onto Ag/Si and Ag/Mn/sub 3/Si/Ag/Si templates has been demonstrated. Due to the evolution from island-like to a continuous film structure as a function of Ag thickness, the ordering and orientation of the FePt films both change with Ag thickness. A continuous [002] Ag film results in a greater L1/sub 0/ phase formation with c-axis oriented both perpendicular to and in the film plane while the island-like Ag template results in less L1/sub 0/ phase formation, but a preferential c-axis orientation in the film plane. On the other hand, the FePt films deposited onto the Ag/Mn/sub 3/Si/Ag/Si template have their c axes aligned perpendicular to the film plane.

Mn 3 Si possesses a D03 structure, which is a bcc derivative structure with nearly the same atomic spacing as Cr and NiAl which have been commonly used for longitudinal magnetic recording underlayers. AG(30 nm)/CoCrTa(40 nm)/Mn3Si(x, x=100, 200, 400 nm)/Ag(75 nm) thin films were sputter deposited onto hydrofluoric acid (HF)-etched Si:(001) substrates at elevated temperature. Compared to the 100 and 200 nm thick Mn3Si samples, the XRD spectrum of the 400 nm thick Mn3Si sample shows a significant increase in the intensity of the Mn3Si(002) peak. This suggests that a high volume fraction of the D03 phase was formed. The CoCrTa(112̄0) peak intensity has been found to increase with Mn3Si thickness. As a result, the in-plane coercivity increases as the volume fraction of the D03 phase increases.

The effects of sputtering argon pressures and sputtering power on the microstructure, texture and magnetic properties of NiAI underlayers on CoCrPt films were investigated. In this paper, the relationship between the sputtering conditions, microstructure, crystallographic texture and magnetic properties of these thin films will be discussed. By controlling the sputtering pressure and sputtering power, the texture and microstructure of NiAI underlayers were found to vary. This in turn was found to influence the magnetic properties of CoCrPt thin films. It was found that 10 mtorr is the optimum pressure to deposit the NiAl thin films to obtain the best magnetic properties for our system. At this argon pressure, the coercivity reached a maximum value because of the strongest CoCrPt (1010) texture and smallest grain size. At lower argon pressures (< 10 mtorr), NiAI tended to have a (110) texture reducing the CoCrPt (1010) texture, which in turn reduced the CoCrPt coercivity and S*. Also, high NiAl deposition pressures (>30 mtorr) yielded larger grains and a weaker CoCrPt (1010) texture, thereby decreasing the coercivity of the CoCrPt films. Increasing the sputtering power has been found to increase the CoCrPt coercivity and S* value. However, the grain sizes of the CoCrPt/NiAl thin films deposited at higher sputtering power were larger than those obtained at lower sputtering power.

The development of crystallographic texture in thin film longitudinal recording media is discussed. Polycrystalline thin films may obtain their crystallographic texture by means of a nucleation process such as epitaxial nucleation on a polycrystalline underlayer or by means of a process involving a preferred growth direction. In this paper we will discuss various epitaxial nucleation textures that are obtained in media produced for magnetic recording. We will discuss the way that the underlayer controls the crystallographic texture of the magnetic layer, as well as methods used to control the texture of the underlayer itself. We give a brief overview of some of our recent findings in the growth of NiAl and FeAl films used for underlayers. Finally we will briefly discuss what we have called the tilted electron beam technique. In this technique selected area electron diffraction patterns are obtained at different angles of tilt and the development of arcs in the patterns is analyzed so as to determine the type and amount of crystallographic texture which is present in the films.

Disordered fcc ~face-centered-cubic !@ 100# fiber-textured CoPt thin films with thicknesses of 20-40 nm were deposited on a nonmagnetic sputtered MgO seed layer with and without a Ag intermediate layer. These were subsequently annealed at 600-750 °C for 5-10 min using rapid thermal annealing ~RTA!. The structural variants were determined to coexist in the in-plane and normal to the plane directions after the RTA process. The MgO underlayer without the intermediate layer revealed strong in-plane anisotropy by magnetic hysteresis measurement. Selected area diffraction ~SAD! by TEM and XRD measurements for these samples confirmed the preferential growth of in-plane variants of c axis compared to the perpendicular direction. High remanence and coercive squareness (S*) were obtained due to strong in-plane texture and especially due to exchange coupling among the grains. Evidence for this was provided by DM curves. Initial magnetization curves for samples annealed above 600 °C, showed the possibility of assembled single domain or domain pinning mechanism but with negligible free wall motion inside of the grains. © 2000 American Institute of Physics. @S0021-8979~00!61008-3#