Patent Application
20140063644
Various embodiments of the present disclosure are generally directed to a magnetic reader that is capable of data access and environmental measurements. In accordance with various embodiments, a magnetic element may be constructed with first and second data transducing elements that are each adapted to selectively read data and measure clearance from an adjacent data storage media.
Data storage devices have advanced towards greater data capacity and faster data access rates, but can be susceptible to magnetic and physical instability. With rotating data storage components, clearance between a magnetic media and a transducing head can be reduced to increase data bit density on the media at the cost of volatility due to environmental conditions. Monitoring of environmental conditions, such as head-disk clearance, may be conducted by processing the readback signal of a data sensor. However, occasional data sensor instability can produce erroneous measurements resulting in data access errors and head-disk interface failure. Thus, there is a continued demand in the industry for increased reliability in environmental measurements such as head-disk clearance.
Accordingly, a magnetic element, such as a magnetic data reader or writer, may be constructed with first and second data transducing elements that are each adapted to selectively read data and measure clearance from an adjacent data storage media. The use of multiple data transducers provides a number of operational and structural options that allow for increased data access reliability and accuracy. One such option is the ability to use a first transducer for data bit access while concurrently measuring head-disk clearance with a second transducer.
Another option constructs the second transducer with a larger physical size and reduced magnetic shielding that is utilized to provide continuous head-disk clearance measurements and occasional redundant data bit sensing. These magnetic element configurations illustrate how multiple data transducers can be tuned to provide increased data access performance, especially in reduced form factor data storage devices.
As an example of an environment in which a magnetic element with multiple data transducers can be practiced,
The transducing portion 100 has an actuating assembly 102 that positions a transducing head 104 over programmed data bits 106 present on a magnetic storage media 108. The storage media 108 is attached to a spindle motor 110 that rotates during use to produce an air bearing surface (ABS) 112 on which a slider portion 114 of the actuating assembly 102 flies to position a head gimbal assembly (HGA) 116, which includes the transducing head 104, over a desired portion of the media 108.
The transducing head 104 can include one or more transducing elements, such as a magnetic writer and magnetically responsive reader as well as one or more environmental sensors, such as a head-disk clearance sensor that may or may not be capable of accessing data, which operate to program and read data from the storage media 108, respectively. In this way, controlled motion of the actuating assembly 102 and spindle motor 110 can 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 surface 114 to selectively write, read, and rewrite data.
The free layers 128 and 130 are each contactingly adjacent a non-magnetic spacer layer 132 that acts to provide a measureable magnetoresistive effect between layers 128 and 130. The coupled lamination of the free layers 128 and 130 to the spacer layer 132 can be characterized as a trilayer due to the lack of any fixed magnetization, such as a reference layer or antiferromagnetic coupling layer. Such lack of magnetization can be offset by the presence of a rear bias magnet 134 adjacent the magnetic stack 122, distal the ABS, that induces the free layers 128 and 130 to a default magnetization that can be overcome when proximal to a data bit, such as data bit 106 of
Configuring a transducing element 120 with a rear bias magnet 134 instead of adding a reference layer in the magnetic stack 122 can reduce the shield-to-shield spacing of the element 120 without sacrificing signal sensitivity and amplitude. Regardless of size and data accessing construction of the magnetic stack 122, a plurality of data transducing elements, such as magnetic element 120, can be placed in a transducing head, like transducing head 104 of
As shown, each transducing reader elements 146, 148, and 150 are disposed between reader features 152 and 154, but such configuration is not liming as the reader features 152 and 154 can be a variety of different components, much like writing feature 144, and can be positioned proximal to one or more transducing elements depending on the magnetic scope intended for the respective elements 146, 148, and 150. The fact that three transducing elements 146, 148, and 150 are used in also not limiting as less or more than three elements can be constructed to provide a wide range of magnetic element 140 embodiments.
In one such magnetic element 140 construction embodiment, the first transducing reader element 146 is configured as a trilayer magnetic stack that is capable of sensing data bits while the second and third transducing reader elements 148 and 150 are configured as magnetoresistive sensors utilizing a fixed magnetic reference layer to sense data. Despite the different reader element configurations, the use of data bit sensitive magnetic stacks for each element 146, 148, and 150 can allow for environmental measurements through processing of the amplitude and harmonic ration of sensed data signals. That is, each transducing reader element 146, 148, and 150 can read data bits and measure environmental conditions such as head-disk clearance.
The utilization of different magnetic stack laminations can allow for cost and manufacturing time efficient construction of a magnetic element 140 as some magnetic stack laminations can be made faster and at less expense than other data bit sensitive laminations. The use of multiple transducing reader elements 146, 148, and 150 that provides the ability to redundantly sense data and measure environmental conditions further allows for the construction of some or all of the elements 146, 148, and 150 with different magnetic and physical tolerances.
For example, the central first transducing reader element 146 may be configured with a reduced size emphasizing accurate data bit sensing while the second and third reader elements 148 and 150 have a greater size and reduced shielding. Such varying reader element configurations can be utilized without detriment to the integrity of data bits or condition measurements due to the redundant data sensing and environmental measurement capabilities provided by having multiple reader elements 146, 148, and 150.
The laterally aligned, along the Z axis, positioning of the transducing reader elements 146, 148, and 150 can allow for efficient magnetic shielding while measuring conditions across relatively large distances, but such a configuration can be altered to accommodate a variety of operating conditions.
The configuration of an actuating assembly 162 with a gimbaled head 164 having multiple reader elements 166 arranged in a substantially triangular shape can mitigate the effects of skew angle and allow for occasional or constant two-dimensional data sensing from different data tracks 168 of the data media 170. That is, the reader elements 166 can be positioned anywhere on the head 164 to allow concurrent reading of data from adjacent data tracks 168 and the alignment of the respective elements with different data tracks 168 regardless of the rotational position of the head 164 with respect to the center of the media 170.
The physical size of the first transducing reader element 182, as defined by the areal extent, can be complemented by a magnetic size tuned with the positioning of at least top 190, bottom 192, left side 194, and right side 196 shields proximal to various portions of the first transducing reader element 182. The size, material, and orientation of the various shields 190-196 are not limited to a particular design, but can be tuned to continuously extend along the first reader width 186 or height 188 to prevent errant magnetic flux from affecting the magnetization of the first or second magnetically free layers 198 and 200.
With the unlimited physical and magnetic configurations possible through tuning of the first transducing reader element 182, the precise construction of such tuned components can be costly in terms of both manufacturing time and materials. While having at least one reader element tuned for precise magnetic and physical size can be present in some embodiments to provide a high degree of data bit sensing accuracy, the use of multiple reader elements may lessen the precision of the physical and magnetic tuning of the first transducing reader element 182.
The utilization of a shielded first transducing reader element 182 can further allow for the other reader elements to be configured with different structural and operational characteristics conducive to increased efficiency. The example embodiment of
The ability to construct the second transducing reader element 184 with greater tolerances for magnetic sensitivity and stability, such as configuring the second reader 184 to use a fixed frequency signal that is lower than the data rate, allows for the second reader element 184 to be tuned, in some embodiments, to specifically detect various operational conditions, such as thermal asperities, head-disk contact, and head-disk clearance. It should be noted that while the second reader element 184 can be tuned in a variety of different manners, the combined function as a transducing element and a sensor provides the ability to selectively operate with redundant operation of the multiple reader elements to read data as well as sense environmental conditions.
For the purposes of this disclosure, the term “transducing element” is meant to describe a magnetic stack lamination capable of sensing data bit present on a rotating data media across an air bearing from the magnetic stack. Furthermore, the term “selectively” is meant to describe the ability to activate, or deactivate, the operation of an element at will. For example, a transducing element that continually senses environmental conditions and reads data is not a selective component. However, a transducing element that reads data and senses environmental conditions for a predetermined time before proceeding to read data or measure environmental conditions would be a selective component.
Various embodiments segment portions of one or both magnetic shields 228 and 230 to provide the ability to selectively use the second and third reader elements 224 and 226 to read data and measure environmental conditions. Such a shield configuration can allow for utilization of the strengths of each magnetic stack configuration without sacrificing data access speed and accuracy. That is, a spin valve may provide a quickly produced magnetic stack capable of detecting a variety of environmental conditions while the tunnel junction may have an increased level of data bit sensing accuracy that is efficiently produced with tolerances and physical size greater than that of the trilayer magnetic stack.
Regardless of the strengths of the various reader element configurations, the ability to use different transducing laminations with varying tolerances, sensitivities, and stability can be tuned, such as by adjusting the distance 232 from the side shields 230 to the external second and third reader elements 224 and 226, to provide a magnetic element capable of sophisticated magnetic reading, such as two-dimensional data sensing, with increased accuracy due to the capability of monitoring environmental conditions and reading data bits both redundantly and separately.
With the magnetic element constructed and in place, the routine 240 can continually or sporadically measure clearance with at least one of the transducing elements in step 242. There is no limit or requirement to the type and manner of clearance measurement as step 242 can use field adjust fly height (FAFH), contact detection, thermal asperity detection, and proximity sensing by one or more of the transducing elements concurrently or successively. The variety of clearance measurement options illustrates how diverse step 242 can be conducted to accommodate a variety of different operational criteria, such as data transfer rates, accuracy, and post-trauma vibrations. In other words, the manner in which step 242 is conducted can be modified, such as from concurrent measurements by each transducing element to a single measurement by one transducing element, on-the-fly without bringing the magnetic element offline.
Regardless of how the clearance between the magnetic element and data storage media is measured in step 242, decision 244 continually monitors the measurements for a change. If no change is detected, the routine 240 returns to step 242 to continue measuring head-media clearance. However, if a change in the clearance is detected, for whatever reason, step 246 determines the validity and extent of the change. In some embodiments, step 246 modifies the clearance measuring manner of the magnetic element by concurrently attaining clearance data from each transducing element of the magnetic element.
The clearance data from step 246 is then evaluated by decision 248 to determine the validity of the change in clearance detected in decision 244. A clearance change that does not meet a minimum threshold advances the routine 240 back to the clearance measurements of step 242 while a verified clearance change above the minimum threshold proceeds to step 250 where the position of the magnetic element in relation to the data storage media is actively adjusted. There is no limitation or requirement as to how such an adjustment takes place, but various embodiments modify clearance through heater variations, actuator speed changes, and media spin rate alterations.
It can be appreciated that routine 240 can continually or sporadically conducted by one or more magnetic elements to monitor and adjust to a predetermined head-media clearance. However, the routine 240 of
With the various structural and operational configurations of a magnetic element with multiple transducing elements that can selectively read data and measure head-media clearance, sophisticated data sensing can increase data accuracy and transfer rates due at least to the ability to access data from multiple transducing elements individually or collectively. The ability to simultaneously read data and measure head-media clearance allows for data accuracy and speed to be maintained during foreseen and unforeseen circumstances. Moreover, the ability to modify the manner in which data and clearance measurements are sensed allows for adaptation and tuning of magnetic element performance to accommodate a variety of different characteristics, such as increased data accuracy. In addition, while the embodiments have been directed to magnetic sensing, it will be appreciated that the claimed technology can readily be utilized in any number of other applications, such as data programming.
It is to be understood that even though numerous characteristics and advantages of various embodiments of the present disclosure have been set forth in the foregoing description, together with details of the structure and function of various embodiments, this detailed description is illustrative only, and changes may be made in detail, especially in matters of structure and arrangements of parts within the principles of the present disclosure to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed. For example, the particular elements may vary depending on the particular application without departing from the spirit and scope of the present technology.
