Patent Application
20120145551
The disclosed process relates to the general field of magnetic read-write heads with particular reference to film preparation and, more specifically, to electroplated magnetic films.
Magnetic read-write heads are commonly fabricated as a single integrated unit. Generally, the read head portion is laid down first. It includes a magnetically free layer whose orientation influences the electrical resistance of the device through spin polarization introduced in either a copper spacer due to the GMR effect (Giant Magneto resistance) or in a very thin insulating layer due to the TMR effect (Tunneling Magnetic Redsistance).
Because it comprises a series of ultra-thin layers, the read head portion has to be formed through use of vacuum technology. The writer portion of the device, however, comprises layers that are relatively thick by vacuum standards. Because of this, electro-deposition offers, in principle, an attractive alternative for the formation of the write head. However, magnetic thin films, as formed according to state of the art electrodeposition methodologies, do not always have, in their as-deposited forms, the magnetic properties necessary for optimum performance
More specifically, films of CoFe or CoNiFe electrodeposited according to the practices of the prior and current art, have been made with either low coercivity or high magnetic saturation but not with both properties in same film. This situation can be remedied to some extend by subjecting the electrodeposited film to a magnetic thermal anneal (typically about 60 minutes at a temperature of at least 200% C in a magnetic field, along the easy axis, of at least 200 Oe). This heat treatment, while effective in terms of improving the magnetic properties, has the unfortunate side effect of destabilizing the read head that is already there.
Thus, there exists a need for a method of forming, through electrodeposition, a film that has the desired magnetic properties in its as-deposited form. i.e does not require a post deposition anneal in order to meet its specifications.
A routine search of the prior art was performed with the following references of interest being found:
U.S. Pat. No. 2,654,703 (Brown) teaches using aryl sufinates in the electrodeposition of bright Ni, Co, and their alloys. U.S. Pat. No. 3,969,399 (Passal) describes adding hydroxy-sulfinate to a plating bath to plate at least one of Ni and Co. U.S. Pat. Nos. 4,014,759 and 4,053,373 (McMullen et al) disclose aromatic sulfinate and aldehyde or dialdehyde used in iron-containing baths to improve plating of alloys of Fe, Ni, Co.
U.S. Pat. No. 6,801,392 (Kawasaki et al) shows a plating bath for FeNi including a sulfate as a surfacant. U.S. Patent Application 2004/0051999 (Yazawa et al) shows controlled composition of a plating bath to form a soft magnetic film. No sulfinate is disclosed.
U.S. Patent Application 2006/0029741 (Hattori et al) describes a sulfinate used as a surfacant in making a magnetic particle-coated material. U.S. Patent Application 2003/0209295 (Cooper et al) teaches electroplating a CoFe film using an aromatic sulfinic acid or a salt thereof. Benzenesulfinic acid is preferred. The electroplating may be performed on a Ru substrate.
It has been an object of at least one embodiment of the disclosed process to provide, through electrodeposition, a magnetic film having, as deposited, both low coercivity and high saturation magnetization.
Another object of at least one embodiment of the present disclosed process has been for said magnetic film to have high corrosion resistance.
Still another object of at least one embodiment of the present disclosed process has been for said film to have low internal stress.
A further object of at least one embodiment of the present disclosed process has been to provide a plating solution and process for depositing said magnetic film.
These objects have been achieved by providing a plating bath that comprises, in solution, all elements that are to be present in said layer, then adding to this plating solution aryl sulfinates in a concentration range of from about 0.05 to 0.3 g/L The resulting films have, as-deposited, a saturation magnetization of at least 24 kG together with a coercivity less than 0.3 Oe.
These films can thus be used for the formation of the write portion of an integrated read-write head. Since the films possess the necessary magnetic characteristics (low coercivity and high saturation magnetization) in their as-deposited form, there is no need for a subsequent magnetic anneal, which would subject the read portion of the device to possible degradation.
a and 2b compare B-H loops for films plated from the invented plating bath with films plated from a prior art bath (i.e without added aryl sulfinate).
a-3d compare B-H loops for FexCoyNiz films plated on different seed layers.
For high recording density, materials with high saturation magnetization, and low coercivity are required. However, materials with high saturation magnetization (greater than 23 kG) usually have a relatively large coercivity as well as poor corrosion resistance, which will limit their application. In the disclosed process, we disclose a new method to overcome these problems by electrodepositing FexCoyNiz films (x=60-71, y=25-35, z=0-5), using an optimized plating bath and a seed layer.
A key feature of the present disclosed process is the addition of organic sulfinates to the plating bath which results in the production of Fe—Co—Ni films having both low coercivity and high saturation magnetization. By choosing the appropriate seed layer (i.e. Ru), the magnetic softness can be further improved (coercivity less than 0.3 Oe).
Although Aryl sulfinates have previously been reported for the electrodeposition of bright Ni, Co, and NiCo alloys to help to refine grain size, they have not been used as a means for controlling the magnetic properties of electrodeposited films.
Of particular importance is that write heads that incorporate such films (i.e. those fabricated according to the teachings of the present disclosed process) do not need to undergo a subsequent high temperature anneal. For a magnetic head, including both a TMJ (tunneling magnetic junction) reader and a write head, the elimination of a later high temperature anneal makes the TMJ reader more stable.
Additionally, the present disclosed process discloses how the addition of a small amount of Ni (<5 atomic %) to a FeCo film improves its corrosion resistance also resulting in films that exhibit unusually low internal stress.
As noted earlier, the present disclosed process is well suited for the formation of the write portion of an integrated read-write head assembly. The latter is schematically illustrated in
Next, magnetizing coil 14 is formed over layer 13 followed by the electrodeposition of second layer of magnetic material 15 over both first layer 13 and coil 14. As before, layer 15 has, as deposited, a saturation magnetization of at least 24 kG and a coercivity less than 0.3 Oe. Layers 13 and 15 are magnetically connected at first end 16 and magnetically separated at the opposite end by write gap 17. The process concludes with the formation of additional magnetic shield layer 18 over layer 15. Thus, formation of the magnetic write head has been completed without subjecting the TMJ read head to a heat treatment.
The composition of the solution used to deposit the films described above is as follows:
The deposition conditions are as follows:
a and 2b compare B-H loops for films plated from the invented plating bath (i.e with added aryl sulfinate) (
Seed layers can affect film nucleation and growth which, in turn, will affect film properties.
The addition of a small amount of Ni (less than 5 atomic %) to Fe-Co films can improve the anti-corrosion properties.
This is a divisional application of U.S. patent application Ser. No. 11/431,261, filed on May 10, 2006, which is herein incorporated by reference in its entirety, and assigned to a common assignee.
| Number | Date | Country | |
|---|---|---|---|
| Parent | 11431261 | May 2006 | US |
| Child | 13400389 | US |
