Stock material or miscellaneous articles – Composite – Of inorganic material
Reexamination Certificate
1999-05-20
2002-06-25
Kiliman, Leszek (Department: 1773)
Stock material or miscellaneous articles
Composite
Of inorganic material
C428S690000, C428S690000, C428S690000, C428S690000, C428S900000, C204S192200, C360S125330
Reexamination Certificate
active
06410170
ABSTRACT:
BACKGROUND
The trend of ever increasing magnetic storage density and data transfer rates requires magnetic materials with superior characteristics. Soft magnetic materials with high magnetic flux density B
s
are of great interest for thin film write head applications. At high operating frequencies, eddy currents in the write head cause a reduction in the permeability of the pole material, which in turn reduces the efficiency of the head.
Lamination of the magnetic pole material with insulation layer is commonly used as a means to suppress the eddy-current loss during the high frequency operation as disclosed in U.S. Pat. No. 5,750,275, by Katz et al., entitled THIN FILM HEADS WITH INSULATED LAMINATION FOR IMPROVED HIGH FREQUENCY PERFORMANCE, issued May 12, 1998, herein incorporated by reference in its entirety. Laminating with an insulative material, however, also reduces the B
s
of the structure.
Recently high B
s
Co-based or Fe-based amorphous alloys with high intrinsic electrical resistivity &rgr; have also received great attention, such as disclosed in U.S. Pat. No. 5,725,685, by Hayakawa et al., entitled SOFT MAGNETIC ALLOY THIN FILM WITH NITROGEN-BASED AMORPHOUS PHASE, issued Mar. 10, 1998. Such alloys, however have relatively low B
s
, typically less than about 15 kG, and often suffer from poor thermal stability and corrosion resistance.
Other work has shown increasing resistivity of FeXN sputtered films using N
2
, but, this work has also shown a corresponding reduction in coercivity. Such work has shown FeXN formed primarily of &agr; phase or body centered cubic Fe, with only a small portion of &ggr; phase or face centered cubic Fe
4
N.
What is desired is a soft magnetic material having high magnetic moment B
s
, low magnetostriction &lgr;
s
, high permeability, high frequency performance, corrosion resistance, and thermal stability.
SUMMARY
A preferred method of the present invention provides an improved thin film for carrying magnetic flux. With the preferred method, the magnetic thin film may be formed by depositing Fe by reactive sputtering using N
2
to form a thin film comprising &agr;-Fe and &ggr;-Fe
4
N. With this method, the relative percentage of &ggr;-Fe
4
N in the deposited film is increased to provide expanded lattice constants for both the &agr;-Fe and the &ggr;-Fe
4
N. Increasing &ggr;-Fe
4
N increases resistivity while expanded lattice constants provide improved coercivity in higher resistivity films.
Increasing the percentage of &ggr;-Fe
4
N to provide expanded lattice constants for both the &agr;-Fe and &ggr;-Fe
4
N may be accomplished by adjusting sputtering power, N
2
gas percentage, a flow rate of N
2
, and substrate bias. In some embodiments, high sputtering power of about 3-4 kW with about 15-30 percent of N
2
may be used to sputter FeX, where X is selected from the group consisting of Rh, Ta, Hf, Al, Zr, Ti, Ru, Si, Cr, V, Sr, Nb, Mo, Ru, and Pd, to provide expanded &agr;-Fe and the &ggr;-Fe
4
N lattice constants.
In preferred methods and embodiments of the present invention, high resistivity low coercivity FeXN thin films are possible. In some embodiments, FeXN films having resistivity values greater than about 50 &mgr;&OHgr;cm, 80 &mgr;&OHgr;cm, 100 &mgr;&OHgr;cm, 115 &mgr;&OHgr;cm, or more, for coercivity values less than about 10 Oe, 5 Oe, or 3 Oe are possible. Furthermore, these results may be obtained for values of B
s
greater than around 12 kG to 17 kG.
Embodiments of the improved thin film of the present invention may be used for pole or shield structures in magnetic heads, such as disk, tape, or other type data storage and retrieval apparatuses, to improve high frequency performance.
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Wang, S., Liu, F., Maranowski,
Chen Yingjian
Qian Chester
Carr & Ferrell LLP
Kiliman Leszek
Read-Rite Corporation
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