Apparatus and method for measuring slider fly height relative to bit patterned media

A slider having a reader and a writer is moved relative to a magnetic bit pattern medium comprising magnetic dots arranged to include a plurality of pre-written servo sectors, data fields defined between servo sectors to which data can be written and erased, and pre-written timing synchronization fields interspersed within the data fields. In some approaches, two different tone patterns are read from one or more of the timing synchronization fields, and fly height of the slider is determined using the two different tone patterns. In other approaches, two odd harmonics are demodulated from a mixed tone pattern read from one or more of the timing synchronization fields, and fly height of the slider is determined using the two odd harmonics.

SUMMARY

According to some embodiments, a method comprises moving a slider having a reader and a writer relative to a magnetic bit pattern medium comprising magnetic dots arranged to include a plurality of pre-written servo sectors, data fields defined between servo sectors to which data can be written and erased, and pre-written timing synchronization fields interspersed within the data fields. The method also comprises reading two different tone patterns from one or more of the timing synchronization fields, and determining fly height of the slider using the two different tone patterns.

In accordance with other embodiments, an apparatus comprises a slider configured to magnetically interact with a magnetic bit pattern medium comprising magnetic dots arranged to include a plurality of pre-written servo sectors, data fields defined between servo sectors to which data can be written and erased, and pre-written timing synchronization fields interspersed within the data fields. A reader of the slider is configured to read two different tone patterns from one or more of the timing synchronization fields. A detector is configured to determine fly height of the slider using the two different tone patterns.

According to further embodiments, a method comprises moving a slider having a reader and a writer relative to a magnetic bit pattern medium comprising magnetic dots arranged to include a plurality of pre-written servo sectors, data fields defined between servo sectors to which data can be written and erased, and pre-written timing synchronization fields interspersed within the data field. The method also comprises demodulating two odd harmonics of a mixed tone pattern read from one or more of the timing synchronization fields, and determining fly height of the slider using the two odd harmonics.

In accordance with some embodiments, an apparatus comprises a magnetic bit pattern medium comprising a plurality of magnetic dots arranged to include a plurality of pre-written servo sectors, a plurality of data fields defined between servo sectors to which data can be written and erased, and a plurality of pre-written timing synchronization fields interspersed within the data fields. The synchronization fields comprise a first tone pattern pre-written to each of the timing synchronization fields and configured to facilitate synchronization of writing to magnetic dots of the data fields. The synchronization fields comprise a second tone pattern different from the first tone pattern and pre-written to at least some of the timing synchronization fields. The first and second tone patterns are configured to facilitate slider fly height determinations.

The above summary is not intended to describe each embodiment or every implementation. A more complete understanding will become apparent and appreciated by referring to the following detailed description and claims in conjunction with the accompanying drawings.

DETAILED DESCRIPTION

Embodiments are directed to apparatuses and methods for determining fly height of a slider moving relative to a bit patterned medium (BPM). Some embodiments are directed to measuring slider fly height using two different tone patterns pre-written to timing synchronization fields interspersed between data fields of a BPM. Other embodiments are directed to measuring slider fly height using two odd harmonics of a mixed tone pattern pre-written to timing synchronization fields interspersed between data fields of a BPM. Further embodiments are directed to concurrently determining fly height of a slider and performing write synchronization using two different tone patterns or two odd harmonics of a mixed tone pattern written to timing synchronization fields interspersed between data fields of a BPM. Some embodiments are directed to a bit patterned medium that includes two different tone patterns pre-written to timing synchronization fields interspersed between data fields. Other embodiments are directed to a bit patterned medium that includes a mixed tone pattern from which two odd harmonics can be demodulated, such that an amplitude of the two odd harmonics is about the same. Further embodiments are directed to a servo writer and servo writing methodology that produces a bit patterned medium of a type disclosed herein.

FIG. 1illustrates an exemplary system100that comprises a magnetic recording medium110, such as a magnetic disk, that may be used in accordance with various illustrative embodiments. The medium110may comprise, for example, a magnetic recording layer deposited on a substrate, as will be understood by those skilled in the art. The medium110also may include other magnetic or non-magnetic layers, such as a soft magnetic underlayer, exchange-coupled layer, lubrication layer, carbon overcoat, etc., which are not explicitly shown. The recording layer may be fabricated using various ferromagnetic materials and alloys, e.g., embodied as thin-film or particulate media, and may be deposited on the substrate using a variety of deposition techniques known in the art in accordance with bit patterned media (BPM) as described herein. The substrate also may be constructed from various materials, such as glass or conventional aluminum-magnesium substrates used for magnetic disks. The system100, such as a disk drive, may also comprise a motor120used to spin the medium110, as well as a head controller130to control a slider140comprising a read-write head.

The read-write head of the slider140reads information from and writes information to the medium110, which is spun by the motor120. The head controller130(e.g., circuitry used to control the track, position, timing, phase, etc. of the reading and writing operations and circuitry) receives information (e.g., data or timing information) from the read-write head of the slider140, and provides information to the read-write head.

The medium110is arranged as a bit patterned medium, which provides patterns of magnetic regions (e.g., “dots” or “islands”) within non-magnetic material (e.g., “troughs”). In bit patterned media, the magnetic material on a disk is patterned into small isolated blocks or islands (referred to herein generally as “dots”) such that there is a single magnetic domain in each island or “bit”. The single magnetic domains can be a single grain or a few strongly coupled grains that switch magnetic states in concert as a single magnetic volume. To produce the required magnetic isolation of the patterned blocks, the regions between the blocks (e.g., troughs) are essentially nonmagnetic. For efficient use of the BPM storage capacity, write operations to BPM should be aligned such that write current transitions are synchronized with the patterns of dots, i.e., efficient use of BPM capacity requires tight synchronization of the write clock to the phase and frequency of the medium itself (i.e., to the dots). The write operations, if not synchronized to the dots, may be attempting to write between the dots on the non-magnetic areas of the medium or dots may be skipped, thereby reducing the effective storage capacity of the media.

Various techniques can be employed to provide for sampled observation of write clock timing offset relative to dot timing when writing, where the timing signals are read from respective timing synchronization fields interspersed within data fields of the medium110. According to various embodiments, the timing synchronization (TS) fields can also be referred to as phase-lock loop (PLL) fields. A control scheme can be employed to adjust the phase of the write clock used in the subsequent data field for writing discerned from calibrations, and, through continually-applied injections, adjusts the frequency of the write clock based on the timing offsets, which are determined using the signals previously read from the TS fields. The write clock timing then coasts in between TS fields, while a write operation continues with a write clock having updated phase and frequency. When the reader arrives at a next TS field, data writing is suspended while timing information is extracted from the TS field.

FIG. 2Aillustrates the format of BPM (e.g., medium110) configured to support the logical format shown inFIG. 2B. In the representative BPM format shown inFIG. 2B, the medium110includes various servo fields/areas210and TS fields220, but makes no assumptions about servo field position relative to the TS fields220. In other words, the TS fields220are decoupled from the servo fields210in terms of positioning and density (number per revolution). In the illustrative example shown inFIGS. 2A and 2B, it is assumed that the TS fields220occur more frequently than the servo fields210.

The servo fields210are radially coherent across the surface of the medium110. In the representative example shown inFIGS. 2A and 2B, the TS fields220are radially coherent within a “zone”225. According to some embodiments, within a zone225, the same number of dots occur between TS fields220, and thus, the radially coherent TS fields220are read at regular dot intervals (where being radially coherent within a zone implies that the same signal may be read from a read head position anywhere across the zone). Since the TS fields220provide a timing reference for the zone225, this per-zone radial coherence is consistent with the patterning of data dots for constant-density recording per-zone. In other words, each data portion230between a pair of TS fields220within a zone225comprises the same number of dots, spaced at a same linear frequency according to the radial position of the zone on the underlying disk surface. Illustratively, the dot pattern of the TS fields220provides readback of a signal that is recorded with a predetermined number of dots per cycle. As will be described hereinbelow, in some embodiments, at least two different tone patterns are recording in the TS fields220to facilitate techniques for determining fly height of the slider140relative to the surface of the medium110. In other embodiments, a single mixed tone pattern is recorded in the TS fields220from which two odd harmonics can be demodulated for determining fly height of the slider140relative to the surface of the medium110. The two odd harmonics can be demodulated by the read channel (e.g., head controller130).

Data are written to and read from the regions230(data fields) between the interspersed TS fields220. It is noted that the TS fields220can be aligned to logical block boundaries to simplify format control, but that such alignment is not necessary. In the representative example shown inFIGS. 2A and 2B, the data fields230are interrupted with the permanently written (e.g., “read-only”), radially coherent TS fields220. The “X's” shown inFIG. 2Billustrate unused areas in the format that roughly match the length of the interspersed TS fields220. These “quiet” fields260correspond to the position of the writer240when the reader250is over the radially coherent TS fields220.

FIG. 2Billustrates a representative view of information stored on a BPM110having interspersed TS fields in accordance with various embodiments. In particular, between conventional servo fields210, one or more TS fields220may be interspersed at predefined intervals within writeable fields230of tracks235(e.g., four tracks235are shown). A read-write head of a slider140is illustrated, with a writer240and a reader250that are separated by a known distance.

According to some embodiments, the TS fields220comprise one of two or more different tone patterns. In other embodiments, at least some of the TS fields220comprise at least two different tone patterns. For example, the different tone patterns can comprise a 2T preamble and a 3T preamble. The 2T and 3T preambles comprise known patterns that produce a periodic read-back waveform with a known period of a specified number of magnetic dots. A 2T preamble, for example, can be represented by four dots recorded with the pattern 1100 (e.g., 2 dots followed by 2 voids). A 3T preamble, for example, can be represented by six dots recorded with the pattern 111000 (e.g., 3 dots followed by 3 voids). The 2T and 3T patterns can be bipolar or unipolar as is known in the art. It is understood that patterns other than 2T and 3T preambles can be pre-written to the TS fields220to facilitate write synchronization and fly height determinations according to embodiments of the disclosure. According to some embodiments, a mixed tone pattern (e.g., a mixture of 1T and 3T tone patterns) is pre-written to at least some of the TS fields220from which two different odd harmonics are demodulated and used for slider fly height determinations. The mixed tone pattern can also be used for write synchronization, in which case the mixed tone pattern would be pre-written to each of the TS fields220.

As previously discussed, and according to some embodiments, when writing data fields230, the signals read from the interspersed TS fields220are sampled for use in updating the phase and frequency of the write clock relative to the medium110. Data writing is suspended during the reading of the TS fields220, to obviate the complications of read-while-write operations and circuitry. Thereafter, data writing is resumed in sections232of the data fields, which can be referred to as “runt” data fields. Note that the length of the runt fields232roughly corresponds to the nominal writer-reader separation (i.e., the distance between writer240and reader250).

Write synchronization implemented using the TS fields220can involve a three-step methodology. First, a TS field220is read by reader250(seeFIG. 2B), and data writing is suspended (thus, quiet field260). Second, write clock phase corrections are calculated, and third, the write clock phase and frequency control is updated. Illustratively, these second and third steps may be executed immediately after TS field220is read, and before the write of the data field230. According to another implementation, these steps may be completed during completion of writing data field230, or may wait until the writer is over the TS field220when data writing is suspended to apply the phase and frequency control update. The controller applies a phase update as a step and a frequency update over the entire interval between TS fields220as a continuously applied phase offset, until the process is repeated at the next TS field220. Additional details of write synchronization using TS fields220according to various embodiments are disclosed in commonly owned, U.S. Pat. No. 7,969,676, which is incorporated herein by reference.

Embodiments of the disclosure are directed to determining slider fly height for bit patterned media using timing synchronization fields that are also used for write synchronization. Some embodiments are directed to determining slider fly height for bit patterned media using timing synchronization fields containing different tone patterns, such as two different single tone patterns. Other embodiments are directed to determining slider fly height for bit patterned media using timing synchronization fields containing a mixed tone pattern, from which two odd harmonics can be demodulated. According to various embodiments, fly height of a slider can be measured using the following Wallace Spacing Loss equation:

A⁢⁢Rd=k⁢⁢ⅇ-2⁢π⁢⁢d⁡(1λfreq1-1λfreq2)d=-12⁢⁢π⁢(1λfreq1-1λfreq2)-1⁢ln⁡(A⁢⁢Rd)+f⁡(k)Δ⁢⁢d=d-dref=-12⁢π⁢(1λfreq1-1λfreq2)-1⁢ln⁡(A⁢⁢RdA⁢⁢Rref)[1]
where ARdis the amplitude ratio at a given head-medium spacing distance, d, k is a constant that, along with f(k), falls out of Equation [1], λfreq1is the write frequency of the first harmonic of a first tone pattern (or the first harmonic of a mixed tone pattern), λfreq2is the write frequency of the first harmonic of a second tone pattern (or the of the mixed tone pattern), drefis the reference head-medium spacing distance (e.g., for head-medium contact), ARrefis the amplitude ratio at the reference head-medium spacing distance, dref, and Δd is the change in spacing distance between d and dref. It is understood that Δd can represent absolute fly height of the slider by using head-medium contact as the reference head-medium spacing distance, dref.

FIG. 3illustrates a track of a bit pattern medium that includes timing synchronization fields containing different tone patterns interspersed between data fields in accordance with various embodiments. In particular,FIG. 3shows a portion of a data track235of a bit pattern medium110bounded by servo sectors or wedges210. Disposed between the servo sectors210is a data field230comprising magnetic dots to which data (e.g., user data) can be written and erased. Interspersed within the data field230is a multiplicity of timing synchronization fields220. In the embodiment shown inFIG. 3, alternating tone patterns, T1and T2, are pre-written to the timing synchronization fields220. In particular, timing synchronization field TSF1contains a first tone pattern, T1, timing synchronization field TSF2contains a second tone pattern, T2, timing synchronization field TSF3contains the first tone pattern, T1, timing synchronization field TSF4(not shown) contains the second tone pattern, T2, and so on. According to some embodiments, the first tone pattern, T1, is a 2T pattern, and the second tone pattern, T2, is a 3T pattern.

The alternating tone patterns, T1and T2, are read by the reader250of the slider140as the track235moves relative to the slider140. After a pair of the alternating tone patterns, T1and T2, has been read by the reader250, a processor of the head controller130is configured to measure the first harmonic of the tone pattern signal amplitudes and calculate fly height of the slider140using Equation [1] above. Slider fly height can be calculated after reading each subsequent pair of alternating tone patterns, T1and T2. In some embodiments, the predetermined number, N (e.g., N=5 or 10), of fly height calculations are used to compute an average slider fly height. Depending on the number of timing synchronization fields220containing different tone patterns (e.g., T1and T2), slider fly height can be calculated a multiplicity of times during each disk revolution (e.g., each data sector).

It is noted that the aforementioned write synchronization operations can be performed concurrently with the fly height computations. For example, a phase detector of the head controller130processes the first tone pattern, T1read from TSF1and computes the phase/frequency of the write clock relative to the magnetic dots of the track235. Updates to the write clock are made in response to reading the second tone pattern, T2, read from TSF2. This process of updating the write clock is repeated using the tone pattern recorded at each of the timing synchronization fields220.

FIG. 4illustrates a track of a bit pattern medium that includes timing synchronization fields containing groups of different tone patterns interspersed between data fields in accordance with other embodiments. According to the embodiment shown inFIG. 4, a track235of a bit pattern medium110includes alternating groups, G1and G2, of timing synchronization fields220. Each group, G1and G2, includes timing synchronization fields220containing the same tone pattern. For example, group G1includes a multiplicity of timing synchronization fields220containing a first tone pattern, T1. Group G2includes a multiplicity of timing synchronization fields to 20 containing a second tone pattern, T2.

As a shown inFIG. 4, a particular group of timing synchronization fields220is disposed between a given pair of servo sectors210, and the different TSF groups alternate between servo sectors210. According to some embodiments, the timing synchronization fields220of group G1containing tone pattern T1follow odd-numbered servo sectors210, while the timing synchronization fields220of group G2containing tone pattern T2follow even-numbered servo sectors210. In the representative example shown inFIG. 4, the first tone pattern, T1, can be a 2T pattern, and the second tone pattern, T2, can be a 3T pattern. As in the case of the previous embodiment, write synchronization operations can be performed concurrently with the fly height computations.

FIG. 5illustrates a track of the bit pattern medium that includes timing synchronization fields containing different tone patterns interspersed between data fields in accordance with further embodiments. According to the embodiment shown inFIG. 5, each timing synchronization field220interspersed within a data field230contains a multiplicity of tone patterns that are used to calculate slider fly height. More particularly, one of the multiplicity of tone patterns is used for fly height determinations, and one of the multiplicity of tone patterns is used for both flight height determinations and write synchronization. It is noted that, according to some embodiments, two different tone patterns of a timing synchronization field220can be used for fly height determinations, and a third tone pattern can be used exclusively for write synchronization.

Referring now to the particular embodiment illustrated inFIG. 5, each of the timing synchronization fields220includes two different tone patterns220aand220b. A first tone pattern220a(T1, e.g., a 2T pattern) is used for write synchronization and fly height determinations. A second tone pattern220b(T2, e.g., a 3T pattern) is used exclusively for fly height determinations. Accordingly, individual timing synchronization fields220that include at least two different single tone patterns can be used for both write synchronization and fly height determinations in accordance with various embodiments.

Inclusion of two different tone patterns220aand220bin each synchronization field220as shown inFIG. 5reduces format efficiency in comparison to the orthogonal tone pattern format shown inFIG. 3. To increase format efficiency, some, but not all, of the synchronization fields220can contain two consecutive (and different) tone patterns. Rather than each synchronization field220containing two different tone patterns, T1, and T2, every nthsynchronization field220can contain the two different tone patterns, T1and T2(e.g., where n is an integer between 2 and 8). For example, if a system requires four updates per data field wedge (data field230defined between two servo sectors210) for write synchronization, but only one fly height measurement per wedge, then each wedge would include three single tone timing synchronization fields220(e.g., T1) and one timing synchronization field220having two consecutive and different single tone patterns (e.g., T1and T2).

FIG. 6shows a track235of a bit pattern medium110that includes a number of timing synchronization fields220provided between servo sectors210. The first two synchronization fields220shown inFIG. 6contain a first tone pattern T1, which are used for write synchronization. A subsequent timing synchronization field220shown inFIG. 6includes two different consecutive tone patterns, T1and T2. For this dual tone synchronization field220, the first tone pattern, T1, is used for write synchronization, and both tone patterns T1and T2are used for calculating slider fly height.

According to other embodiments, another technique for measuring slider fly height involves demodulating two odd harmonics of a single mixed-tone pattern read from a timing synchronization field220. For example, the first and third harmonics of a single tone pattern of a timing synchronization field220can be used to calculate fly height using Equation [1] above, such that the first frequency in Equation [1] is the first harmonic and the second frequency in Equation [1] is the third harmonic. However, since the third harmonic magnitude is much smaller than the first harmonic magnitude, measurement error is introduced at a low signal-two-noise ratio (SNR) condition. According to one approach, a mixed tone pattern that combines a 1T tone pattern and a 3T tone pattern provides comparable energy intensity between the first and third harmonics. It is noted that a 1T tone pattern or preamble can be represented by two dots recorded with the pattern 10 (e.g., 1 dot followed by 1 void).

For example, a mixed tone pattern of 111010 or 101000 for a unipolar timing synchronization field220can be used, where 1 represents a magnetic dot, and 0 represents a void or absence of a magnetic dot. Referring once again toFIG. 3, each of the timing synchronizing fields220can be pre-written with the same single mixed tone pattern (e.g., T1) interspersed within the data fields230of each track235. As such, the tone pattern T2shown for TSF2inFIG. 3would instead be replaced with the mixed tone pattern T1.

FIG. 7Ashows the amplitude of a single tone pattern 111000111000 as a function of time, andFIG. 7Bshows the amplitude of the first and third harmonics of this single tone pattern. It can be seen inFIG. 7Bthat the amplitude of the third harmonic is significantly smaller than that of the first harmonic.FIG. 8Ashows the amplitude of a mixed tone pattern 111010 as a function of time, andFIG. 8Bshows the amplitude of the first and third harmonics of this mixed tone pattern. It can be seen inFIG. 8Bthat the amplitude of the third harmonic is about the same as that of the first harmonic. It is noted that, since the mixed tone pattern has frequency components other than the one of interest useful for timing acquisition, these frequency components may dilute the pattern's timing information value. As such, the timing synchronization field220may be increased in length to compensate for the loss, which reduces format efficiency.

The following methodologies can be implemented using timing synchronization fields of a bit pattern medium in accordance with various embodiments.FIG. 9Ais a flow chart illustrating a method for determining slider fly height relative to a bit patterned medium in accordance with some embodiments. The method shown inFIG. 9Ainvolves moving902a slider relative to the bit pattern medium comprising pre-written servo sectors, data fields between servo sectors, and pre-written timing synchronization fields interspersed within the data fields. The method also involves reading904two or more different tone patterns from one or more of the synchronization fields. The method further involves determining906fly height of the slider using the two or more different tone patterns.

FIG. 9Bis a flow chart illustrating a method for determining slider fly height relative to a bit patterned medium in accordance with other embodiments. The method shown inFIG. 9Binvolves moving912a slider relative to a bit pattern medium comprising pre-written servo sectors, data fields between servo sectors, and pre-written timing synchronization fields interspersed within the data fields. The method also involves demodulating914two odd harmonics of a single mixed-tone pattern read from one or more of the timing synchronization fields. The method further involves determining916fly height of the slider using the two odd harmonics.

FIG. 10is a flow chart illustrating a method for determining slider fly height relative to a bit patterned medium in accordance with various embodiments. The method shown inFIG. 10involves moving1002a slider relative to the bit pattern medium comprising pre-written servo sectors, data fields between servo sectors, and pre-written timing synchronization fields interspersed within the data fields. The method involves reading1004a first tone pattern from the current timing synchronization field, reading1006a second tone pattern from the next timing synchronization field, and determining1008fly height of the slider using the two different tone patterns. A check1010is made to determine if a predetermined number, N (e.g., N=5 or 10), of the first and second tone patterns has been read. If not, the slider advances1012to the next timing synchronization pattern, and the processes of blocks1004-1010are repeated. When the predetermined number, N, is reached, and average slider fly height is determined1014using the fly height determinations1008.

FIG. 11is a flow chart illustrating a method for determining slider fly height relative to a bit patterned medium in accordance with various embodiments. The method shown inFIG. 11involves moving1102a slider relative to the bit pattern medium comprising pre-written servo sectors, data fields between servo sectors, and pre-written timing synchronization fields interspersed within the data fields. The method involves reading1104first tone patterns from a first group of timing synchronization fields, and reading1106second tone patterns from a second group of timing synchronization fields. The method also involves determining1108fly height of the slider using the groups of first and second tone patterns. A check1110is made to determine if a predetermined number, N, of the first and second tone pattern groups has been read. If not, the slider advances1112to the next group of timing synchronization fields, and the processes of blocks1104-1110are repeated. When the predetermined number, N, is reached, an average slider fly height is determined1114using the fly height determinations1108.

FIG. 12is a flow chart illustrating a method for determining slider fly height relative to a bit patterned medium in accordance with various embodiments. The method shown inFIG. 12involves moving1202a slider relative to the bit pattern medium comprising pre-written servo sectors, data fields between servo sectors, and pre-written timing synchronization fields interspersed within the data fields. The method involves reading1204a first tone pattern from a current timing synchronization field, and reading1206a second tone pattern from the same timing synchronization field. The method also involves determining1208fly height of the slider using the first and second tone patterns. A check1210is made to determine if a predetermined number, N, of the first and second tone patterns has been read. If not, the slider advances1212to the next timing synchronization pattern, and the processes of blocks1204-1210are repeated. When the predetermined number, N, is reached, and average slider fly height is determined1214using the fly height determinations1208.

FIG. 13is a flow chart illustrating a method for determining slider fly height relative to a bit patterned medium in accordance with various embodiments. The method shown inFIG. 13involves moving1302a slider relative to the bit pattern medium comprising pre-written servo sectors, data fields between servo sectors, and pre-written timing synchronization fields interspersed within the data fields. The method involves reading1304a first tone pattern from a current timing synchronization field, and determining1306if the current timing synchronization field includes a second tone pattern. If not, the slider advances1308to the next timing synchronization field and the processes at blocks1304and1306are repeated. If the current timing synchronization field includes the second tone pattern, the method involves reading1310this second tone pattern and determining1312fly height of the slider using the first and second tone patterns. A check1314is made to determine if a predetermined number, N, of the first and second tone patterns has been read. If not, the slider advances1308to the next timing synchronization pattern, and the processes of blocks1304-1314are repeated. When the predetermined number, N, is reached, and average slider fly height is determined1316using the fly height determinations1312.

FIG. 14is a flow chart illustrating a method for determining slider fly height relative to a bit patterned medium and performing write synchronization in accordance with various embodiments. The method shown inFIG. 14involves moving1402a slider relative to the bit pattern medium comprising pre-written servo sectors, data fields between servo sectors, and pre-written timing synchronization fields interspersed within the data fields. The method involves reading1404two different tone patterns from one or more of the timing synchronization fields. The method also involves synchronizing1406writing to magnetic dots of the data field following the timing synchronization field using at least one of the tone patterns. The method further involves determining1408fly height of the slider using the two different tone patterns.

FIG. 15is a flow chart illustrating a method for determining slider fly height relative to a bit patterned medium and performing write synchronization in accordance with various embodiments. The method shown inFIG. 15involves moving1502a slider relative to the bit pattern medium comprising pre-written servo sectors, data fields between servo sectors, and pre-written timing synchronization fields interspersed within the data fields. The method involves reading1504a first tone pattern from the current timing synchronization field, and determining1506if the current timing synchronization field includes a second tone pattern. If so, the second tone pattern is read1508from the current timing synchronization field. If the current timing synchronization field does not include a second tone pattern (as tested at1506) or after a second tone pattern has been read from the current timing synchronization field (as performed at1508), the method involves synchronizing1510writing to magnetic dots of the data field following the timing synchronization field using the first tone pattern. The method further involves determining1512fly height of the slider using the two different tone patterns. A check1514is made to determine if a predetermined number, N, of the first and second tone patterns has been read. If not, the slider advances1516to the next timing synchronization pattern, and the processes of blocks1504-1514are repeated. When the predetermined number, N, is reached, and average slider fly height is determined1518using the fly height determinations1512.

Various modifications and additions can be made to the disclosed embodiments discussed above. Accordingly, the scope of the present disclosure should not be limited by the particular embodiments described above, but should be defined only by the claims set forth below and equivalents thereof.