Perpendicular magnetic recording medium having a multi-layer interlayer that includes BCC material

Perpendicular magnetic recording media and methods of fabricating perpendicular magnetic recording media are described. The perpendicular magnetic recording medium of one embodiment includes a soft magnetic underlayer (SUL), an interlayer, and a perpendicular magnetic recording layer. The interlayer comprises a layer formed from a first material (e.g., NiWCr) having a face-centered-cubic (FCC) structure, a layer formed from a second material (e.g., Cr) having a body-centered-cubic (BCC) structure, and a layer formed from a third material (e.g., Ru) having a hexagonal-close-packed (HCP) structure.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention is related to the field of magnetic disk drive systems and, in particular, to a perpendicular magnetic recording medium having an interlayer formed from multiple layers. More particularly, the interlayer is formed from a layer of FCC material (e.g., NiWCr), a layer of BCC material (e.g., Cr), and a layer of HCP material (e.g., Ru).

2. Statement of the Problem

One type of recording medium presently used in magnetic recording/reproducing apparatuses is a longitudinal magnetic recording medium. A longitudinal magnetic recording medium includes a magnetic recording layer having an easy axis of magnetization parallel to the substrate. The easy axis of magnetization is the crystalline axis that is aligned along the lowest energy direction for the magnetic moment. Another type of recording medium is a perpendicular magnetic recording medium. A perpendicular magnetic recording medium includes a magnetic recording layer having an easy axis of magnetization oriented substantially perpendicular to the substrate. Hexagonal-close-packed (HCP) Co-alloys are typically used as the magnetic recording layer for both longitudinal and perpendicular recording. The easy axis of magnetization for these materials lies along the c-axis or <0001> direction.

The perpendicular magnetic recording medium is generally formed with the following layers on a substrate, a soft magnetic underlayer (SUL), an interlayer, a perpendicular magnetic recording layer, and a protective layer for protecting the surface of the perpendicular magnetic recording layer. The soft magnetic underlayer (SUL) serves to concentrate a magnetic flux emitted from a main pole of a write head and to serve as a flux return path back to a return pole of the write head during recording on the magnetic recording layer. The interlayer serves to control the size of magnetic crystal grains and the orientation of the magnetic crystal grains in the magnetic recording layer. The interlayer also serves to magnetically de-couple the SUL and the magnetic recording layer.

The interlayer may be formed from a single layer of material, such as a layer of Ru that has an HCP structure. The interlayer may alternatively be formed from multiple layers. For example, a common interlayer comprises a layer of Ru formed on a seed layer, such as Ta, NiFe, NiW, etc. The seed layer is commonly formed from a face-centered-cubic (FCC) material with the layer of Ru (having the HCP structure) formed on the FCC material. One particular interlayer comprises a seed layer of NiW or another Ni-based alloy, a first layer of Ru deposited at a lower pressure, and a second layer of Ru deposited at a higher pressure.

One problem with many present interlayers for perpendicular magnetic recording media is that they include significant amounts of Ru, which is an HCP material. The thickness of Ru in a common interlayer can reach 200 Å or more. As the cost of Ru and other HCP materials increases, the cost of fabricating perpendicular magnetic recording media unfortunately also increases.

SUMMARY OF THE SOLUTION

Embodiments of the invention solve the above and other related problems with an interlayer of a perpendicular magnetic recording medium that includes less Ru (or other HCP material) than present interlayers. The interlayer as provided herein is formed from multiple layers including a layer formed from a face-centered-cubic (FCC) material (e.g., NiWCr), a layer formed from a body-centered-cubic (BCC) material (e.g., Cr), and a layer formed from a hexagonal-close-packed (HCP) material (e.g., Ru). The BCC material advantageously replaces some of the HCP material in the interlayer without affecting performance. Because the BCC material has a lower cost than the HCP material, such as Ru, perpendicular magnetic recording media may be fabricated at a lower cost without degrading performance. The addition of some BCC materials, such as Cr, may also help with corrosion resistance in the media.

One embodiment comprises an interlayer of perpendicular magnetic recording media. The interlayer includes a first layer formed from a first material having a FCC structure. The interlayer also includes a second layer formed from a second material having a BCC structure. The interlayer also includes a third layer formed from a third material having a HCP structure. The BCC material in the interlayer replaces some of the HCP material without degrading performance. At the same time, the BCC material, such as Cr, is less expensive than an HCP material, such as Ru, which allows for more cost effective fabrication of perpendicular magnetic recording media.

In another embodiment, a perpendicular magnetic recording medium includes, among other layers, a soft magnetic underlayer (SUL), an interlayer, and a perpendicular magnetic recording layer. The interlayer includes a FCC layer, a BCC layer, and a HCP layer. In one particular example of the interlayer, the FCC layer is formed from a Ni-based material (e.g., NiWCr), the BCC layer is formed from a Cr-based material (e.g., Cr), and the HCP layer is formed from a Ru-based material (e.g., Ru).

The invention may include other exemplary embodiments described below, such as associated methods of fabricating perpendicular magnetic recording media.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1illustrates a magnetic disk drive system100in an exemplary embodiment of the invention. Magnetic disk drive system100includes a spindle102, a perpendicular magnetic recording medium104, a motor controller106, an actuator108, an actuator arm110, a suspension arm112, and a recording head114. Spindle102supports and rotates a perpendicular magnetic recording medium104in the direction indicated by the arrow. A spindle motor (not shown) rotates spindle102according to control signals from motor controller106. Recording head114is supported by suspension arm112and actuator arm110. Actuator arm110is connected to actuator108that is configured to rotate in order to position recording head114over a desired track of perpendicular magnetic recording medium104. Magnetic disk drive system100may include other devices, components, or systems not shown inFIG. 1. For instance, a plurality of magnetic disks, actuators, actuator arms, suspension arms, and recording heads may be used.

When perpendicular magnetic recording medium104rotates, an air flow generated by the rotation of magnetic disk104causes an air bearing surface (ABS) of recording head114to ride on a cushion of air at a particular height above magnetic disk104. The height depends on the shape of the ABS. As recording head114rides on the cushion of air, actuator108moves actuator arm110to position a read element (not shown) and a write element (not shown) in recording head114over selected tracks of perpendicular magnetic recording medium104.

The perpendicular magnetic recording medium104is shown as a disk inFIG. 1. However, a perpendicular magnetic recording medium as discussed can take on other forms in other embodiments.

FIG. 2is a cross-sectional view illustrating one exemplary embodiment of perpendicular magnetic recording medium104. Perpendicular magnetic recording medium104includes a soft magnetic underlayer (SUL)205, an interlayer210, and a perpendicular magnetic recording layer215. The layers shown inFIG. 2may be deposited on a substrate (not shown) or on multiple other layers (not shown) previously deposited on a substrate. Perpendicular magnetic recording medium104may include other layers not shown inFIG. 2, such as a cap layer, an overcoat layer, etc. For instance, a cap layer may be formed on perpendicular magnetic recording layer215from a material such as CoPtCrB. An overcoat layer may be formed on the cap layer to protect perpendicular magnetic recording layer215against damage if the recording head happens to contact the perpendicular magnetic recording medium104.

SUL205acts in conjunction with the write head to increase the perpendicular field magnitude and improve the field gradient generated by the write head passing over the perpendicular magnetic recording medium104. SUL205may be formed from CoFeTaZr or another type of material. Interlayer210controls the orientation and grain diameter of perpendicular magnetic recording layer215, and also acts to de-couple SUL205and perpendicular magnetic recording layer215. Perpendicular magnetic recording layer215comprises one or more materials that have an easy axis of magnetization oriented substantially perpendicular to the substrate. Perpendicular magnetic recording layer215is typically formed from a Co-alloy and may contain elements such as Cr and Pt as well as oxides such as SiO2. One example of perpendicular magnetic recording layer215comprises CoPtCr—SiOx.

In this embodiment, interlayer210is formed from multiple layers of material having different crystallographic structures.FIG. 3is a cross-sectional view illustrating one exemplary embodiment of interlayer210. InFIG. 3, interlayer210includes a first layer301formed from a material having a FCC structure, such as a FCC(111) structure. The material forming the first layer301may be a Ni-based material having the FCC structure, examples of which are NiW, NiCr, NiWCr, NiFeCr, and NiFeW. A Ni-based material means any material solely or partially formed from Ni. The first layer301may have a thickness of about 5-10 nanometers.

Interlayer210also includes a second layer302formed from a material having a BCC structure, such as a BCC(110) structure. The material forming the second layer302may be a Cr-based material having the BCC structure, examples of which are Cr, CrMo, CrV, CrTi, CrW, CrMoB, CrMoC, CrMoSe, CrTi, CrV, and MoCr. A Cr-based material means any material solely or partially formed from Cr. The second layer302may have a thickness of about 3-15 nanometers.

Interlayer210also includes a third layer303formed from a material having a HCP structure, such as a HCP(00.2) structure. The material forming the third layer303may be a Ru-based material having the HCP structure, examples of which are Ru, RuCr, and RuTi. A Ru-based material means any material solely or partially formed from Ru. The third layer303may have a thickness of about 3-15 nanometers. The terms “first”, “second”, and “third” are used to distinguish between layers of different material, and are not necessarily indicative of a particular order of the layers. Also, interlayer210may include more layers than those illustrated inFIG. 3.

The second layer302of BCC material may be multi-layer itself.FIG. 4is a cross-sectional view illustrating another exemplary embodiment of interlayer210. InFIG. 4, the second layer302ofFIG. 3is formed from two layers of BCC material. The first layer401of BCC material may serve as a crystallographic enhancement layer. As an example, the first layer401may comprise a layer of Cr or a Cr alloy (CrX) having a low concentration of a doping element (X), such as Mo, Ti, V, W, Ta, Mn, or another element. The atomic percentage of the doping element (X) in the Cr alloy may be between about 5 to 30%.

The second layer402of BCC material may serve as a grain size control layer. As an example, the second layer402may comprise a layer of a Cr alloy (CrX or CrXY) having a higher concentration of a doping element. For instance, the Cr alloy (CrX) may have a doping element (X), such as Mo, Ti, V, W, Ta, Mn, or another element. The Cr alloy (CrXY) may additionally have the doping element (Y), such as B, Si, O, N, or another element. The atomic percentage of the doping element (X) in the Cr alloy may be between about 5 to 30%, and the atomic percentage of the doping element (Y) in the Cr alloy may be between about 5 to 10%. The second layer302may include more layers of BCC material in other embodiments.

Interlayer210may comprise other layers than those shown inFIGS. 3-4.FIG. 5is a cross-sectional view illustrating another exemplary embodiment of interlayer210. InFIG. 5, interlayer210includes the first layer301formed from a material having a FCC structure. Interlayer210also includes the second layer302formed from a material having a BCC structure. Interlayer210also includes the third layer303formed from a material having a HCP structure. These layers resemble the layers illustrated inFIG. 3. However inFIG. 5, interlayer210also includes a fourth layer504formed from a material having an HCP structure. The fourth layer504is formed between the first layer301(the FCC layer) and the second layer302(the BCC layer). The material forming the fourth layer504may be a Ru-based material having the HCP structure, examples of which are Ru, RuCr, and RuTi. Although four layers are shown inFIG. 5, interlayer210may comprise more or less than four layers in other embodiments.

For the embodiments shown inFIGS. 3-5, interlayer210includes a layer of BCC material that replaces some of the HCP material used in many other interlayers. For instance, assume that a prior interlayer includes 200 Å of HCP material, such as Ru. According to the embodiments herein, some of the 200 Å of HCP material will be replaced with BCC material, such as Cr. For instance, interlayer210may include 90 Å of BCC material and 110 Å of HCP material. The thickness of the interlayer210does not change, but the amount of HCP material used is almost cut in half. The reduction in HCP material causes a corresponding reduction in cost of fabrication for the perpendicular magnetic recording medium104due to the higher cost of the HCP material.

The BCC material works well in interlayer210as the lattice of the BCC material matches well with both of the FCC material and the HCP material. With the BCC material replacing some of the HCP material in interlayer210, interlayer210still effectively controls the size of magnetic crystal grains and the orientation of the magnetic crystal grains in perpendicular magnetic recording layer215. Interlayer210also effectively serves to magnetically de-couple SUL205and perpendicular magnetic recording layer215. If a BCC material such as Cr is used in interlayer210, perpendicular magnetic recording medium104will also exhibit a higher resistance to corrosion.

FIGS. 6-7illustrate possible methods of fabricating the perpendicular magnetic recording medium104.FIG. 6is a flow chart illustrating one exemplary method600of fabricating perpendicular magnetic recording medium104. In step602, SUL205is formed (seeFIG. 3) such as by depositing material for SUL205on a nonmagnetic substrate or on other layers previously deposited. In step604, a first layer301of interlayer210is formed (seeFIG. 3). The first layer301is formed from a material having a FCC structure, such as a Ni-based material. In step606, a second layer302of interlayer210is formed (seeFIG. 3). The second layer302is formed from a material having a BCC structure, such as a Cr-based material. In step608, a third layer303of interlayer210is formed (seeFIG. 3). The third layer303is formed from a material having a HCP structure, such as a Ru-based material. In step610, perpendicular magnetic recording layer215is formed (seeFIG. 2) such as by depositing material for perpendicular magnetic recording layer215. The material for perpendicular magnetic recording layer215may comprise CoPtCr—SiOx or another material. Method600forms the perpendicular magnetic recording medium104illustrated inFIG. 3. There may be other layers of material deposited than those described in method600.

To form the perpendicular magnetic recording medium104illustrated inFIG. 4, step606of method600would include two steps of depositing BCC material. The first step may comprise forming a layer of BCC material that serves as a crystallographic enhancement layer. The second step may comprise forming another layer of BCC material that serves as a grain size control layer. Exemplary compositions of these layers of BCC material are provided above.

FIG. 7is a flow chart of another exemplary method700of fabricating perpendicular magnetic recording medium104. Method700is substantially similar to method700in forming SUL205, a first layer301(FCC material) of interlayer210, a second layer302(BCC material) of interlayer210, a third layer303(HCP material) of interlayer210, and perpendicular magnetic recording layer215(seeFIG. 5). Method700includes the additional step702where a fourth layer504of interlayer210is formed (seeFIG. 5). The fourth layer404is formed from a material having a HCP structure, such as a Ru-based material. Method700forms the perpendicular magnetic recording medium104illustrated inFIG. 5. There may be other layers of material deposited than those described in method700.

FIG. 8is a graph illustrating the performance of a perpendicular magnetic recording medium using the interlayer210provided herein. Assume for this example that interlayer210includes a first layer301of NiW (FCC structure), a second layer302of Cr (BCC structure), and a third layer303of Ru (HCP structure). Graph800inFIG. 8illustrates the coercivity of the interlayer for different thicknesses of NiW and Cr. A coercivity measurement indicates the quality of the magnetic layer growth in the perpendicular direction. A high coercivity (Hc) represents a good crystalline orientation.

As a reference point, graph800illustrates the coercivity of a typical interlayer formed from NiW(70)/Ru(90)/Ru(90) (a FCC/HCP interlayer), where the thicknesses referred to are in Angstroms. The coercivity of this reference point is about 4900 Oe. Graph800also illustrates data points802for NiW(x)/Cr(90)/Ru(110) (a FCC/BCC/HCP interlayer). As x increases above about 20 Å, the coercivity raises above 4900 Oe. At about 70 Å, the coercivity is about 5300 Oe. This indicates that the FCC/BCC/HCP interlayer provides a good crystalline orientation even better than the FCC/HCP interlayer traditionally used.

Graph800also illustrates data points804for NiW(52)/Cr(x)/Ru(110). As x increases above about 20 Å, the coercivity raises above 4900 Oe again. At about 70 Å, the coercivity is between 5200 and 5300 Oe. This again indicates that the FCC/BCC/HCP interlayer provides a good crystalline orientation even better than the FCC/HCP interlayer traditionally used.