Head fields of asymmetric recording heads

Head fields of asymmetric recording heads have been measured using 5000:1 enlarged models. From these measurements the head field gradients have been derived and are discussed in view of the role of this quantity in the recording write process.     

Accurate approximation of fields and spectral response functionsfor perpendicular recording heads

Solutions for the magnetic potential in rectangular regions with simple boundary conditions are used to approximate the two-dimensional potential in the head face plane of a recording head. This method of approximation can be applied to any recording head with rectangular corners, in the presence of an underlayer. The slot approximation is demonstrated for ring heads and shielded (magnetoresistive) pole heads. The quarter plane approximation is given for application to finite-length heads. Estimates of the field components and the spectral response function are derived from the approximate potential. The simple slot approximation is shown to be at least as accurate as other, often more complicated, methods of approximation. Most significantly, both the slot and the quarter-plane approximations are easy to apply and need no prior knowledge of the head field of the particular geometry under consideration     

Side fringing fields and write and read crosstalk of narrow magnetic recording heads

In magnetic recording systems the side fringing fields of magnetic recording heads are responsible for crosstalk from adjacent tracks and eventually for partial erasure of adjacent tracks, thereby limiting the attainable track density. In this paper we derive analytical expressions for the magnetic field near the side of a recording head and calculate the cosine transform of the longitudinal field component, with the head side angle and gap length as parameters. The field of a head of zero width is also considered. Due to the side fringing field the written track is somewhat wider than the geometrical head width; the increase in width being approximately proportional to the maximum field strength in the recording medium and the head-to-medium distance. The amplitudeuof the read crosstalk signal from an adjacent, infinitesimally narrow track is calculated and it appears that it can be approximated byu/u_{0} = 0.5 exp (-2pi x/lambda), where u0is the on-track signal (with zero head-to-medium spacing),xis the distance between track and head side, and λ is the wavelength. Maximum track densities are calculated for a specified crosstalk-to-signal ratio and a given head width and wavelength. For a wavelength of 10 μm, a head width of 5 μm, and a crosstalk of -20 dB, the track density is limited to about 130 tracks/mm, assuming a track width equal to the head width. When the track is taken to be 5 μm wider than the head to account for the effects of the write process, no guardband at all is needed for -20 dB crosstalk and the limit to the track density is 100 tracks/mn.     

Total magnetic fields and read characteristics of infinite length pole piece magnetic recording heads

Magnetic recording head fields generated by current distributions of zero total current flux are calculated considering the two topological possibilities for the current elements being either external to infinite permeability pole pieces or contained entirely within the pole pieces. The frequency response for each of these field configurations is determined by application of the fast Fourier transform.     

Characterization of magnetic recording heads for drive-specificapplications

Window margin, time interval and waveform analysis techniques that better describe salient on-track performance issues are described. Many of these techniques can be extended to accommodate the addition of off-track and peak shift effects     

Properties of side-shielded read heads in longitudinal and perpendicular recording

Side-shielded (SS) read heads were fabricated, and their magnetic track widths were calculated and measured. The measurements in longitudinal recording show that SS heads exhibit sharper profiles compared with side-unshielded heads. To examine the effect of side shielding, we studied the dependence of the magnetic read width on write density using calculations and experiments. The calculations indicate that the SS head can reduce the skirt of the microtrack profile even at low densities, while the side-unshielded head cannot. This result was qualitatively found in an experiment. We also studied the SS effect in perpendicular recording and found better performance. The calculations predict that SS can strongly reduce the skirt of the microtrack profile even in perpendicular recording. We observed a sharper profile in an SS head compared with a side-unshielded one.     

Numerical analysis of ferrite recording heads with complex permeability

Numerical methods based on finite differences are applied to the analysis of ferrite recording heads in which the permeability is complex and flux leakage effects are significant. The methods described allow computation of head efficiency, inductance, loss angle, and phase shift. As a specific example, the analysis is performed for a reduced track width version of the Memorex 3650 head for a wide range of the real and imaginary parts of the permeability. Using published values for the frequency dependence of the complex permeability, the frequency dependence of the head performance is estimated. Some experimental data are presented and compared to the theoretical predictions.     

High density recording with perpendicular Co-Cr-Nb media and ring heads

Effective double layer structure was investigated by adding Nb to the sputtering source of Co-Cr thin film perpendicular magnetic recording tapes. The output from the tapes was measured with a ring head through to the short wavelength, λ50=0.19 μm (D50=267KFRPI).     

Properties of one-sided probe heads on double-layer perpendicular recording media

The perpendicular recording mode is still a candidate for obtaining higher densities. Best recording results on a double-layer (DL) medium must be expected from using a probe head (PH). This contribution provides an analysis of the write-read performance of one-sided PHs that do not use an auxiliary pole on the back of the medium. Analytical as well as numerical models were used to calculate the effects of saturation and medium thickness on the write fields. Experimental verification of the modeling results was obtained by measuring the wavelength response of many W-shaped PHs on DL media. Combining this with the calculated response, we obtained a semi-empirical relation between the pole nulls, pole thickness and the pole-to-backlayer distance. It reveals a PH behaviour very different from a ring head (RH). The pole thickness calculated from the measured pole-null wavelengths showed a very close agreement with the optically determined value. The calculated head efficiencies are very small, as was confirmed experimentally, and need improvement before the PH has an output comparable with a RH.     

Batch fabrication of thin film magnetic recording heads: A literature review and process description for vertical single turn heads

Several publications in the past have discussed the potential of batch fabricated thin film heads. Most of these publications dealt with theoretical predictions. Only a few discussed fabrication techniques and reported on the write and read test results. This paper describes a fabrication process for single turn thin film heads of vertical configuration. The process utilizes well known evaporation, plating, and photolithographic techniques. It is simple, inexpensive, and amenable to batch fabrication. Heads fabricated using this process were shown to write and read on a disk, moving at 40 m/s (1575 in/s) with ∼6 Kfr/cm. Dynamic test results reported in a paper by Valstyn and Shew corroborate the earlier prediction. This paper also discusses and compares advantages and disadvantages of the single turn heads of a vertical configuration with those of a horizontal configuration.     

Calculation of temperature fields

A method is discussed for solving heat-transfer problems in various regions for variable thermophysical characteristics. The method is based on the reduction of boundary-value problems of mathematical physics to infinite systems of linear algebraic equations which can be solved by the reduction method.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 32, No. 6, pp. 1109–1114, June, 1977.     

Analytic expression for the fringe field of finite pole-tip length recording heads

Previous computations based on a conformal transformation are used as a guide in selecting a plausible magnetic scalar potential at the surface of the head. An analytic expression for the horizontal component of the field is obtained from this potential. Certain characteristics of the potential and field are discussed.     

Decoding of digital magnetic recording with longitudinal magnetization of a tape from a magneto-optical image of stray fields

For digital magnetic recording of encoded information with longitudinal magnetization of the tape, the connection between the domain structure of a storage medium and magneto-optical image of its stray fields obtained using a magnetic film with a perpendicular anisotropy and a large Faraday rotation has been studied. For two-frequency binary code without returning to zero, an algorithm is developed, that allows uniquely decoding of the information recorded on the tape based on analysis of an image of stray fields.     

Development of magnetoresistive shielded heads simulation techniques using conformal mapping

Conformal mapping techniques have been applied to develop an alternative method to take into account the influence of finite shield geometry in the properties of magnetoresistive (MR) reading heads.     

Comparison of ring and pole head magnetic fields

Idealized mathematical models of the magnetic fields generated by ring and single-pole heads are examined. In each case, more accurate Fourier coefficients than have been published previously are provided. However, the main purpose is to consider, in a more rigorous manner than has been presented before, the correspondence between the fields of ring and pole heads. Ranges of parameters and areas of the domain are identified for which the fields are almost identical. In the region of each geometry occupied by the recording medium, the similarities were less clear     

Magnetic properties, microstructures, and corrosion resistance ofhigh-saturation FeMoN and FeRhN films for recording heads

We have investigated high-saturation FeMoN and FeRhN films, deposited by radio frequency-diode reactive sputtering on alumina-TiC substrates, for inductive head applications. A minimum coercivity of ~1.2 Oe is obtained in (Fe_97.8Mo_2.2)N films at a N ₂/Ar flow ratio of ~6.2%. A minimum coercivity of ~1.6 Oe is obtained in (Fe_96.9Rh_3.1)N films at a N₂/Ar flow ratio of ~4.6%. The films mainly consist of α-Fe phase and γ'-Fe₄N phase; The magnetic properties of these films are stable under easy axis field annealing up to 350°C. Addition of Rh or Mo to FeN has resulted in a significant improvement in corrosion resistance over that of FeN. The localized corrosion resistance of FeRhN and FeMoN can be comparable to that of Permalloy. In contrast, their intrinsic corrosion resistance is inferior to that of Permalloy, but it can be adjusted and controlled by pH level     

Effect of pole-tip size on perpendicular recording head remanence

To aid understanding the physical mechanisms responsible for the perpendicular write head remanent field and thereby improve the write head design, we studied the remanence of single-pole perpendicular recording heads with trailing shield by using a contact scanning recording tester. We used two different pole-tip size heads in the study. We found that the remanence areas of the heads tested usually locate at the trailing edge corners of the pole tip. We also found that the remanence areas of both types of heads are also the head field easy-rising areas when the heads are driven by low write currents. Additionally, the current level that leads to remanence is the same for both types of heads. However, the remanence of the small pole-tip heads can be demagnetized by a much lower amplitude reverse current than that of the large pole-tip heads.     

Calculation of the switching constant of magnetic recording media

We studied the dynamic switching time in two classes of media by considering two different particle orientation distribution functions. We calculated the switching constant directly from the Landau-Lifshitz-Gilbert equation of motion, which was chosen to simulate the dynamic properties of the media. A strong linear relation between the reciprocal of the switching time and the difference between the applied and anisotropy fields is illustrated. In media for which experimental results are available, the values we obtained here agree within a factor of 2