Magnetic reader with tuned anisotropy

Various embodiments may be generally directed to a stack capable of reading magnetic data bits. Such a stack can have a non-magnetic spacer layer disposed between a magnetically free layer and a synthetic antiferromagnet (SAF) where the SAF is configured with an anisotropy tuned to a non-normal direction with respect to an air bearing surface (ABS).

SUMMARY

Various embodiments of the present disclosure are generally directed to a stack that is capable of magnetic data bit sensing.

In accordance with some embodiments, a magnetic reader can have a non-magnetic spacer layer disposed between a magnetically free layer and a synthetic antiferromagnet (SAF) where the SAF is configured with an anisotropy tuned to a non-normal direction with respect to an air bearing surface (ABS).

DETAILED DESCRIPTION

Continuing emphasis for larger capacity, faster data storage devices has stressed the form factor in which data storage elements can be reliably manufactured and operated. One such data storage element is a magnetic data reader, which responds to data bits programmed on a data storage media to create a data signal. An increase in data bit density for storage media can elevate data capacity, but with the added consequence of inducing unwanted data signal amplitude loss and instability. Hence, industry is striving to provide magnetic data readers capable of providing increased data signal amplitude and stability in small form factor, increased data bit density data storage devices.

Accordingly, a magnetic reader may have a non-magnetic spacer layer disposed between a magnetically free layer and a synthetic antiferromagnet, where the synthetic antiferromagnet is configured with an anisotropy tuned to a non-normal direction with respect to an air bearing surface. The ability to tune the anisotropy of portions of the magnetic reader can maintain magnetic stability and interaction between the synthetic antiferromagnet and the magnetically free layer, which can produce greater data signal amplitude while decreasing magnetic asymmetry.

While a magnetic reader with tuned anisotropy can be practiced in a variety of non-limiting environments,FIG. 1generally displays a data transducing portion100of a rotating data storage environment. The transducing portion100is configured with an actuating assembly102that positions a transducing head104over programmed data bits106present on a magnetic storage media108that is attached to, and rotates about, a spindle motor110to produce an air bearing surface (ABS)112. The speed in which the spindle motor110rotates allows a slider portion114of the actuating assembly102to fly on the ABS to position a head gimbal assembly (HGA)116, which includes the transducing head104, over a desired portion of the media108.

The transducing head104can include one or more transducing elements, such as a magnetic writer and magnetically responsive reader, which operate to program data to and read data from the storage media108, respectively. In this way, controlled motion of the actuating assembly102and spindle motor110can modulate the position of the transducing head both laterally along predetermined data tracks (not shown) defined on the storage media surfaces and vertically as measured perpendicularly to the media surface114to selectively write, read, and rewrite data.

FIG. 2shows a cross-sectional block representation of an example magnetic data reader120capable of being used in the transducing portion100of a data storage device shown inFIG. 1. While not required or limited to the configuration shown inFIG. 2, the magnetic reader120has a magnetic stack122disposed between electrode layers124and magnetic shields126on an air bearing surface (ABS). The magnetic stack122can be configured as a variety of different data bit sensing laminations, such as a magnetoresistive, tunnel magnetoresistive, and spin valve, but in some embodiments is constructed as a sensor with a magnetically free layer128and fixed magnetization reference structure130coupled to opposite sides of a non-magnetic spacer layer132.

The magnetic orientation of the free layer128and reference structure130acts to provide a measurable magnetoresistive effect when an external data bit is encountered. Various embodiments fix the magnetization of the reference structure130via connection with an antiferromagnetic layer. However, inclusion of such an antiferromagnetic layer can add to the shield-to-shield spacing134of the reader120which can provide difficulties in sensing data bits from reduced form factor data storage devices employing heightened data bit densities and reduced data track widths. With the removal of an antiferromagnetic layer from the magnetic stack122, the reader's shield-to-shield spacing134can be reduced, but at the cost of introducing magnetic instability as the reference structure130may be left unsupported, which can correspond with magnetization tilting and asymmetry resulting in overall data signal amplitude loss.

Configuring the free layer128with a magnetization direction that differs from the reference structure130may compensate for adverse effects resulting from the removal of an antiferromagnetic layer by stabilizing magnetizations in both the reference structure130and free layer128. Setting the magnetization direction of the various layers in the reader120can be accomplished in several different, non-limiting, manners such as by setting the intrinsic anisotropy of the reference structure130and free layer128to provide magnetization directions that are perpendicular and parallel to an air bearing surface (ABS) of the reader120, respectively.

More specifically, the free layer128may be formed with an intrinsic anisotropy that maintains bipolar magnetization in a plane aligned along the Z-axis while a reference layer136and pinned layer138of the reference structure130are formed with intrinsic anisotropies that align the fixed magnetizations respectively along the X-axis. With the magnetizations of the reference and pinned layers136and138antiferromagnetically coupling across a SAF spacer layer140and being out of phase with the magnetization of the free layer128, magnetic stability of the reader may be optimized to decrease magnetic asymmetry and increase data signal amplitude.

The ability to tune the intrinsic anisotropy of the magnetic stack122layers may combine with the tuning of the size of the reference structure130and free layer128to optimize the reader's120performance to accommodate various environmental conditions, such as data bit density and data readback rate.FIG. 3displays a block representation of a cross-section of an example magnetic stack150tuned in a variety of manners to provide predetermined data sensing performance. As shown, the magnetic stack150is configured as a lamination of layers each having a predetermined stripe height152measured from the ABS along the X-axis.

Various embodiments can tune the stripe height152of one or more of the free154, reference156, and pinned158layers individually or collectively to produce multiple different stripe heights152for the magnetic stack. Regardless of whether the stripe height152is tuned in any way, each of the magnetic stack150layers can be optimized for thickness, as measured along the Y-axis. For example, the free layer154can be tuned to a first predetermined thickness160that differs from second and third predetermined thicknesses162and164corresponding to the reference156and pinned158layers, respectively.

In some embodiments, the reference156and pinned158layers are tuned in view of the overall thickness of the reference structure166that includes the SAF spacer layer168to balance the magnetizations of the respective layers with respect to the tuned anisotropy strengths and directions. That is, the predetermined thicknesses162and164of the reference156and pinned158layers, such as 2.6 nm and 3.1 nm respectively, can be chosen in relation to the intrinsic anisotropy, such as 400 Oe, of each layer156and158to balance magnetic asymmetry and provide magnetic stability despite the lack of an antiferromagnetic layer being present in the stack150.

Tuning the thicknesses160,162, and164and stripe height152of the respective magnetic stack150layers can be done in isolation or in combination with tuning the intrinsic anisotropy of one or more of the layers.FIGS. 4 and 5each generally illustrate block top view representations of example layers180,190, and200each capable of being used in a magnetic stack, such as magnetic stack122ofFIG. 2. Layer180shows how the intrinsic anisotropy can be constructed with a magnetization direction182that is parallel to the ABS and the Y-axis while layer190displays how the magnetization direction192can be oriented along the X-axis, perpendicular to the ABS.

While the orientation of various layers in the same magnetic stack may be tuned with intrinsic anisotropies causing magnetization directions that are normal, parallel or perpendicular, to the ABS, tuning the magnetization direction to a non-normal orientation202, as displayed by layer200, can increase data signal amplitude, especially when paired with other magnetic stack layers optimized for thickness and anisotropic strength. It should be noted that the term “non-normal” will be understood to describe an angular orientation not equaling zero or ninety degrees.

It is to further be understood that the manner in which the intrinsic anisotropy and magnetization directions are constructed are not limited to a particular process and may be formed and tuned in a variety of different means. As a non-limiting example, the azimuth angle of grazed oblique deposition onto a seed layer can be used to create tuned intrinsic anisotropy corresponding to a 150 degree non-normal magnetization direction, as generally shown by magnetization202in layer200ofFIG. 4and more specifically by the magnetizations of layers displayed inFIG. 5. A review ofFIG. 5reveals how the non-normal magnetization direction of layer200can provide a more uniform magnetization profile throughout the layer than the normal magnetization directions of layers180and190.

No matter how the intrinsic anisotropy and magnetization direction are formed, the tuning of a non-normal magnetization direction can be done for magnetic stack layers individually or collectively, which can precisely optimize magnetic stack performance as illustrated by the data ofFIG. 6. InFIG. 6, the effects of different magnetization directions are graphed in relation to data signal amplitude for a 200 Oe intrinsic anisotropy by solid line210and for a 400 Oe intrinsic anisotropy by segmented line212. With the data from lines210and212, a magnetic stack, and specifically the reference structure of a magnetic reader, can be tuned and optimized to produce data signal amplitudes conducive to various small form factor data storage environments.

A tuned embodiment resulting from the data ofFIG. 6may configure pinned and reference layers of a reference structure each with 400 Oe intrinsic anisotropies and 150 degree non-normal magnetization directions to produce roughly a 131% data signal amplitude, which contrasts sharply with a magnetic stack having non-tuned anisotropy and no antiferromagnetic layer to support the magnetization of the reference structure. The combination of the tuned intrinsic anisotropy direction and magnitude with the tuned thickness and stripe height can provide optimized magnetization asymmetry and stability that allows for relaxed anisotropy amplitude with lower shield-to-shield spacing in addition to greater data signal amplitude.

FIG. 7provides an example flowchart of a reader fabrication routine220that maps how a magnetic stack can be tuned in accordance with various embodiments. The routine220may initially deposit a magnetic shield and electrode on a substrate in step222. The electrode layer can extend from an air bearing surface to a stripe height that is less than or equal to the stripe height of the shield and, in some embodiments, can be configured as a seed layer with material and surface roughness conducive to producing intrinsic anisotropy in a subsequently deposited layer.

Step224then forms a pinned layer on the electrode layer that has a predetermined intrinsic anisotropy magnitude and direction with respect to the air bearing surface. A SAF spacer layer is subsequently deposited on the pinned layer in step226to provide antiferromagnetic coupling between a reference layer and the pinned layer as well as providing a potential seed layer for constructing the reference layer with predetermined intrinsic anisotropy in step228. That is, the SAF spacer layer formed in step226may have a thickness and non-magnetic material that provides antiferromagnetic coupling and a substrate that may be roughed as a seed layer to aid in producing the intrinsic anisotropy of the reference layer in step228with a second magnitude and direction that may be the same, or differ, from the anisotropic magnitude and direction in the pinned layer.

With the formation of the reference layer completing the construction of the fixed magnetization reference structure, step230deposits a non-magnetic spacer layer atop the reference layer with a thickness allowing data sensing between the magnetization of the free layer and the reference structure. Various embodiments next form a magnetically free layer on the non-magnetic spacer layer in step232with a third intrinsic anisotropy that has different magnitude and direction than the anisotropy of both the reference and pinned layers. Formation of the magnetically free layer in step232is then followed by the deposition of a top electrode and shield in step234.

It should be mentioned that while routine220successively deposits layers in a particular sequence, such sequence is not required or limiting as the magnetic stack can comprise any number and orientation of layers. For example, the magnetically free layer may be formed before the reference and pinned layers of the reference structure so that the magnetic stack is flipped in comparison to a stack produced from routine220.

With the ability to tune the various magnetic stack layers by optimizing the intrinsic anisotropy to produce predetermined magnetization directions and magnitudes, the magnetic operation of the magnetic stack can be tailored to provide predetermined ratios of magnetic stability, data signal amplitude, and magnetic asymmetry. The routine220, however, is not limited only to the steps and decisions provided inFIG. 7as any number of steps can be added, omitted, and modified to accommodate the fabrication of a precisely tuned magnetic reader.

It can be appreciated that the configuration and material characteristics of the magnetic reader described in the present disclosure allows for tuned data sensing conducive to high data bit density, small form factor data storage devices. The ability to tune portions of a magnetic stack with a differing anisotropies and magnetization directions may provide increased magnetic stability and reduced asymmetry that promotes higher data signal amplitude. Moreover, the utilization of non-normal intrinsic anisotropy in at least the reference structure of a magnetic stack can provide enough magnetic stability to remove an antiferromagnetic layer and reduce the overall physical size of the magnetic stack. Additionally, while the embodiments have been directed to magnetic sensing, it will be appreciated that the claimed invention can readily be utilized in any number of other applications, including data storage device applications.