A. Morisako

Ba-ferrite thin film rigid disk for high density perpendicular magnetic recording

A magnetoplumbite type of hexagonal Ba-ferrite films, whose c-axis of crystallites is well oriented perpendicularly to the film plane, have been prepared by means of a conventional rf diode sputtering system. Morphological and crystallographic characteristics of sputtered Ba-ferrite films depend strongly on preparation conditions such as the distance between target and substrate d T-S and partial pressure of oxygen gas P O2 during the deposition. Ba-ferrite films with smooth surface are prepared at the extended d T-S in the region of low P O2 . Read/write characteristics of Ba-ferrite thin film deposited on thermally oxidized silicon wafer with radius of two inches were evaluated with ring type head. Recording density D 50 of Ba-ferrite thin film rigid disk depends strongly on Δθ 50 . In this work, D 50 of 110 and 190 kfrpi for Δθ 50 of 4.8 and 2.8°, respectively, have been attained.

Synthesis of ferromagnetic τ phase of Mn‐Al films by sputtering

Mn‐Al films have been prepared by dc magnetron sputtering and their crystallographic characteristics, magnetic properties, electrical resistivity, and internal stress have been investigated. The films deposited when substrate temperature Ts was below 100 °C and above 170 °C exhibit a high‐temperature e phase and β‐Mn–like structure, respectively. Films of a ferromagnetic τ phase were synthesized with Mn content in the range of 58–62 at. % and Ts of about 150 °C. Existence of CuAu‐type superstructure in the τ phase was confirmed by a change of electrical resistivity ρ of deposited films. The films deposited at a Ts of about 150 °C exhibit minimum value of 180 μΩ cm. Lattice constant a and c of the tetragonal τ‐phase crystallites in the films were in the range of 3.582–3.592 A and 3.941–3.968 A, respectively, while those of the bulk alloy were 3.580 and 3.940 A, respectively. The maximum value of saturation magnetization of the films was 120 emu/cc, being as small as about one fourth of that of bulk alloy. ...

The effect of oxygen gas pressure on Ba-ferrite sputtered films for perpendicular magnetic recording media

Barium ferrite (BaM) sputtered films with a small c-axis dispersion angle, Delta theta /sub 50/, and smooth surface are needed for ultra-high-density perpendicular recording. These properties, which depend strongly on oxygen partial pressure, P/sub O2/, during sputtering, were studied experimentally. In the low-P/sub O2/ region (below 0.003 mTorr at total P (P/sub Ar/+P/sub O2/) of 3.7 mTorr), a spinel phase was formed and exhibited a rough surface with large grain. In the mid-P/sub O2/ (0.003-0.2 mTorr) and high-P/sub O2/ (0.3-3.7 mTorr) regions, a mixed spinel and a BaM single phase were formed, respectively. The films deposited at high P/sub O2/ exhibited large perpendicular anisotropy and consisted of needle-like particles, while those deposited at medium P/sub O2/ exhibited perpendicular anisotropy of about 1.0 kOe. The H/sub k perpendicular to / of these films was about 10 kOe, and they had a very smooth surface and small Delta theta /sub 50/. >

Influences of sputtering gas pressure on microtexture and crystallographic characteristics of Ba-ferrite thin films for high density recording media

Ba-ferrite films with small c-axis dispersion angle Δθ 50 are suitable for ultrahigh density recording media. The dependences of partial oxygen gas pressure P O2 and total discharge gas pressure P Total on the characteristics of Ba-ferrite films were clarified. It was found that there were three regions, where films were composed of single layer of spinel type ferrite(P O2 ≤0.002mTorr), mixed layer of spinel and magnetoplumbite type ferrites ( 0.003 \leq P_{O2} \leq 0.2 mTorr) and single layer of magnetoplumbite type ferrite (P O2 >0.3 mTorr). In the range of P 02 between 0.005 and 0.2 mTorr, spinel-like ferrite layer plays very important role as an underlayer to decrease the Δθ 50 of the Ba-ferrite layer. Films deposited at relatively low P O2 and P Total exhibit very smooth surface and Δθ 50 as small as 2.5\sim3.5\deg .

Iron nitride thin films prepared by facing targets sputtering

The iron nitride thin films have been deposited using a facing targets sputtering (FTS) system and a conventional dc diode magnetron sputtering system, and their crystallographic characteristics and magnetic properties have been investigated. The total gas pressure (PN2+PAr) was set at 2 mTorr. The films deposited by the FTS system without heating the substrate at PN2 below 0.3 mTorr possessed α‐Fe‐like structure with an increased lattice constant. At PN2 of around 0.5 mTorr, a two‐phase mixture of α‐Fe and Fe2–3N was formed in the films prepared in the FTS system, while ζ‐Fe2N phase was formed in the films prepared by dc magnetron sputtering. The films prepared by FTS at PN2 of 0.1 mTorr possessed α‐Fe and γ’‐Fe4N structures when a substrate temperature (Ts) was in the range from 80 to 300 °C. The films deposited at Ts of about 150 °C possessed a saturation magnetization (Ms) of about 1700 emu/cm3, which is larger than that of pure iron films and coercivity (Hc) of about 1.5 Oe.

Ba-Ferrite Films Prepared by Sol-Gel Pyrolysis Method

Crystallographic and magnetic properties of Ba-ferrite films prepared by a sol-gel pyrolysis method were investigated. A solution of Ba- and Fe-nitrates dissolved in ethylene glycol became a gel with an appropriate viscosity by ultrasonic stirring at 80°C. Films were spin-coated onto SiO2/Si substratesr dried and then heated in air at various temperatures. In films prepared at a composition ratio of Fe2/Ba=5, a drying temperature Td=250°C and a crystallizing temperature TC=800°C, single-phase Ba-ferrite was obtained, and the magnetization at 10 kOe field ¿10k and coercivity Hc were 47.0 emu/g and 3 ~ 4 kOe, respectively. Films prepared at Td=250°C had smooth surfaces without any cracks. In thin films of thickness 900Å, preferred orientation of the c-axis was observed.

Read/write characteristics of a Ba-ferrite sputtered disk

Ba-ferrite thin film rigid disks with various c-axis dispersion angle Δθ 50 and various film thickness have been prepared by rf diode sputtering. Read/write characteristics of Ba-ferrite disks were evaluated by means of ring type Mn-Zn ferrite head. Reproduced wave forms of isolated magnetization transition showed dipulse and dipulse ratio depended on recording current. Dipulse ratio decreased with increase of recording current. PW 50 ( pulse width at half height of reproduced output at low density ) and λ 50 ( recorded wave length at D 50 )depended on Δθ 50 of Ba-ferrite thin film and both PW 50 and λ 50 increased with increase of Δθ 50 . Over-write ratio of -31dB has been obtained at 2F of 40 kfrpi. D 50 of disks with Δθ 50 of 2.5∼2.8° depended on the film thickness. 88, 95 and 100 kfrpi in D 50 for the thickness of 0.26, 0.16 and 0.066 μm, respectively, have been ontained with a head with gap length of 0.4 μm.

Current-Induced Domain Wall Motion in TbFeCo Wires With Perpendicular Magnetic Anisotropy

Current-induced domain wall motion in TbFeCo wires with perpendicular magnetic anisotropy has been directly observed by Kerr microscope. The moving direction of domain wall is opposite to the current direction, which is in agreement with the spin torque transfer theory. The critical current density found in TbFeCo is lower than 107 A/cm2, which is an order smaller than in other metallic materials reported so far. In addition, the critical current density gets increased with the increase of the pinning potential in TbFeCo thin film, which is also consistent with the theoretical prediction for a pinning dominant mechanism.

c-axis orientation of hexagonal ferrite films prepared by RF diode sputtering

Abstract The structure and properties of Ba-ferrite films have been investigated. The c -axis of hexagonal crystalline of films deposited at T s of 700°C by rf diode sputtering is perpendicularly oriented to the film plane with Δθ 50 below 3°. At the initial stage of depositions, a spinel type of ferrite film is formed. Hexagonal ferrite film grows on this film about 300 A thick.

Sputtered Mn-Al-Cu films for magnetic recording media

Ferromagnetic τ phase of Mn-Al-Cu films have been prepared by dc magnetron sputtering and their crystallographic characteristics, magnetic properties and recording characteristics have been investigated. In binary Mn-Al films, the stability of τ phase is very poor and saturation magnetization Ms as low as about 120 emu/cc. To improve the stabilty of this phase and increase the Ms, Mn was partially substituted by Cu. Ms increased from 120 to 300 emu/cc with increase in Cu content of up to 23 at%. Coercivity Hc decreased with increase of Cu content in the films. τ and κ phase were synthesized at Cu content below 10 at% and above this content, respectively. MnAlCu thin film sputtered disks have been prepared and their recording characteristics have been investigated. Typical recording density D 50 of MnAlCu disk was 59 kfrpi.