Search

A simple energy surface model is introduced to explain single domain particle switching under sub-Stoner-Wohlfarth fields. The criterion is that if the initial energy exceeds the subsequent energy barrier maximum, then the particle can reverse. Reversal will occur only for small damping constants and short field rise times, so the magnetization dynamics explores a sufficiently large portion of the energy surface. The results are confirmed by micromagnetic analyses and are consistent with both large scale micromagnetic simulation and experimental data. This effect may be utilized for ultrahigh density (1 Tbit/in[SUP2]) and ultrahigh data rate magnetic recording (>2 Gbit/s). [ABSTRACT FROM AUTHOR]

Track edge effects in tilted and conventional perpendicular recording are analyzed. The write fields are calculated utilizing a three dimensional micromagnetic simulation that includes both the write pole and the soft underlayer. The dynamic reversal time and thermal stability of the recording layer are analyzed using a recent model involving mode analysis and the optimal collective reversal barrier. For conventional perpendicular recording, the effect of the write field angle at the track edge is to lower the medium energy barrier, which increases the guard-band width. For tilted perpendicular recording, the guard band is decreased due to an energy barrier increase caused by the write field angle. [ABSTRACT FROM AUTHOR]

Poisson's equation is solved exactly to obtain the medium demagnetization field for both a single pole head and a single pole with a trailing shield (shielded single pole) head designs in perpendicular recording. To write an isolated transition, for the semi-infinite single pole head, head imaging can be neglected when calculating the demagnetization field. To the semi-infinite shielded single pole head, when the pole separation is reduced, perfect imaging from both the head and the soft magnetic underlayer is a good approximation. [ABSTRACT FROM AUTHOR]

Micromagnetic simulations have been performed to compare the recording performance of oriented media (M[sub r]=1.50) with planar isotropic media in longitudinal recording. With no exchange, oriented medium exhibits substantially less dc noise power thus larger signal-to-noise ratio (SNR). But with increasing linear density, the oriented medium shows larger nonlinear amplitude reduction, larger nonlinear transition shift, and less SNR advantage. At finite exchange, there is no substantial SNR difference between oriented and isotropic medium. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Dynamic switching time in longitudinal thin film media is studied by numerical simulation. An exponential head field with various rise times is assumed. A linear relation (with slope S[sub w]) to correlate the inverse of switching time and the maximum reverse field is found to apply only for rise times larger than 0.3 ns. The switching constant S[sub w] increases with increasing rise time, decreasing damping constant, and increasing intergranular exchange. A wide range of S[sub w], from about 250 to about 3500 Oe ns, is found for rise times between 0.05 and 1 ns. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Micromagnetic simulations of planar isotropic magnetic thin film recording media are performed to study initial magnetization reversal processes in response to pulses with linear and exponential ramps. Linear ramps lead to smaller zero-crossing times T[sub 0] than exponential ramps due to the more rapid field increase during the pulse ramps. It is shown that T[sub 0] increases substantially when the pulse amplitude is less than about half the anisotropy field, in which case pulse overshoots are effective to reduce T[sub 0]. In addition, the effects of exchange coupling and gyromagnetic damping are examined. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Presents information on a study which examined the feasibility of reversing single bit per particle media at high density and data rate in magnetic recording systems. Experimental results; Conclusion.

Investigates the nonlinear distortion in the playback signals in magnetic recording (MR) due to the readback process of MR heads. Explanation for the nonlinear response of an asymmetric MR head; Details of the experimental techniques used; Linear analysis of MT heads.

We compare several different detection and equalization methods for bit patterned media recording channels .We consider a scheme that utilizes a joint-track equalization technique followed by a Viterbi detector. For certain recording densities, simulation results show that it has essentially the same performance as an optimal detector but with reduced detection complexity. Furthermore, it outperforms another scheme of the same complexity previously described in the literature. [ABSTRACT FROM AUTHOR]

A dual-layer patterned element magnetic recording medium design is presented that is expected to satisfy areal densities at 10 Tb/in². Each element consists of a small high anisotropy initial layer on top of which is deposited on an exchange-coupled soft layer of approximately equal thickness that extends in the recording direction almost to an adjacent element. This design has two distinct advantages. Reversal by precessional switching will occur for realistic record head field rise times (100-200 ps). Thermal stability for such small elements is maintained by hard section anisotropy fields that are an order of magnitude larger than the reversal field. Here, reversal mechanisms and system design are discussed in detail. [ABSTRACT FROM AUTHOR]

To optimize a high-density magnetic recording system, one needs to know the tradeoffs between various components of the system including the read/write transducers, the magnetic medium, and the read channel. In this paper, we consider a channel model characterized by three parameters: the replay pulse width T50, the transition jitter noise standard deviation σ J,, and the signal-to-electronic-noise ratio SNRWG. We utilize information-theoretic tools to determine the acceptable region for the channel parameters T50 and σ J when optimal detection and linear coding techniques are used. This paper is an extension of a similar analysis for a system that utilized a minimum mean-squared error (MMSE) equalizer, a Viterbi detector, and a Reed-Solomon (RS) code. Our main conclusion is that there is a considerable potential gain to be achieved by using improved detection and coding schemes as compared with the present system. [ABSTRACT FROM AUTHOR]

Presents a study that measured and analyzed signal-dependent noise spectra of metal particle tapes. Background on the use of magnetoresistive heads and fine metal particle tapes in increasing recording densities in modern tape recording systems; Details on the pattern used to eliminate tape speed variations; Analysis of various noise mode contributions for different coating thicknesses.

Part III. Focuses on a study which describes magnetic simulations to examine the effect of intergranular exchange on thermal stability of dibit transitions in magnetic recording, perpendicular media. Analysis on the energy barrier of coupled perpendicular grains; Evaluation of the thermal decay of dibit transitions; Conclusion.

Describes micromagnetic simulations that examine the effect of intergranular exchange on thermal stability of dibit transitions in magnetic recording. Information on the macromagnetic simulation models used; Comparison on the varying magnetic orientation ratios, thermal decays of dibit patterns; Evaluation on the thermal decays of dibit and square wave patterns in perpendicular media.

Part II. Describes micromagnetic simulations to examine the effect of intergranular exchange on thermal stability of dobit transitions in magnetic recording with slightly oriented longitudinal media. Function used for simulating the c axis preferential alignment; Information on the thermal decay of dibit transitions; Conclusion.

Focuses on a study which investigated the potential of extending conventional magnetic recording technology to a one terabit per square inch density using a simple model. Information on the recording simulation procedure; Analysis on the isolated transition and 31-bit pseudorandom sequence; Discussion on the off-track performance.

Presents a study that theoretically examined the playback characteristics of a giant magnetoresistive head for perpendicular recorded magnetization transitions with a soft underlayer. Shape of the isolated signal for different permeabilities of the underlayer; Formulation of an analytical expression for the pulsewidth Tsub[50] and Dsub[50]; Determination of a formula for the transition-noise-limited signal-to-noise ratio.

Describes simulations of servo position error signal (PES) in a perpendicular recording system. Evaluation of the effect of medium noise on the PES detection; Dependence of the servo PES on the average-medium grain in-plane area; Comparison of the PES of longitudinal recording systems with that of perpendicular systems.

Provides information on a study that investigated the thermal dynamic effects for short write times and long storage times in thin film media. Background on the media for ultra high areal density recording and high data rate; Methodology; Results and discussion.

Focuses on a study which used a magnetic analysis method to determine the mean magnetic spacing of a contact head/tape interface. Background of the magnetic analysis technique; Experimental technique and results; Head/tape spacing obtained from numerical simulations.

Micromagnetic simulations have been performed to compare longitudinal thin film media with and without a grain size distribution. Hysteresis loops and dibit recording are evaluated for various exchange interactions. The results show that the grain size distribution reduces effects of both intergranular exchange and magnetostatic interactions. [ABSTRACT FROM PUBLISHER]

Tape surface roughness noise is a large component of medium noise in high-density tape recording systems. Here, the results of tape surface roughness characterization by both mechanical and magnetic measurements are presented. The goal is to measure and compare both RMS roughness variance σ and roughness correlation length l. The results show that the magnetic recording determination of σ and l agrees extremely well with the mechanical measurements. [ABSTRACT FROM PUBLISHER]

Patterned media elements comprising coupled magnetically hard and soft sections of different horizontal size, referred to as ledge elements, are characterized by several unique properties. These elements allow for remarkably reduced reversal fields, which are an order of magnitude below the Stoner-Wohlfarth limit. They also allow for precessional reversal to occur for practical field rise times (100–200 ps), which are two orders of magnitude larger than those in the case of homogeneous elements (∼2 ps). These attractive properties are obtained even for elements of small height (4–8 nm). Patterned media implementing such ledge elements can allow for recording densities above 10 Tbit/in2. [ABSTRACT FROM AUTHOR]

A micromagnetic model for the writing process in perpendicular magnetic recording is developed to study the effect of the soft underlayer on the dynamic reversal of the recording layer. The upper part of the soft material is discretized micromagnetically, each spin following LLG dynamics; the remaining part has infinite permeability. The validity of the model is tested in the static case. Dynamically, high-frequency spin motion is observed in the soft layer. Nevertheless, the field inside the data layer follows the time dependence of the input waveform. [ABSTRACT FROM AUTHOR]

A micromagnetic Monte Carlo simulation is developed to study the thermal decay and erasure process for perpendicular recording media. The switching probability is calculated based on both the energy barrier analysis and the master equation. The results show that for current head media combination at 1 Tb/in², the ensure is severe for the neighboring tracks unless the bit-aspect ratio is increased. The magnetic write width for both side shielded (SS) and no side shield (NSS) head is about the same. The erase band for the SS write head is significantly smaller (20 nm less) than that for the NSS head, corresponding to 10 nm or 12% track pitch reduction. [ABSTRACT FROM AUTHOR]

Presents a study which examined thermal decay of interacting magnetic grains in perpendicular thin film media for magnetic recording. Discussion of thermal-dynamic reversal in coupled grains; Analysis of two nonidentical perpendicular grains; Results.

Deals with a study that obtained an analytic solution for the distribution of the magnetic orientation of two grains. Importance of understanding the magnetic characteristics of thin film media in the field of magnetic recording devices; Methodology; Results and discussion.

Deals with a study that investigated the effects of three anisotropy sources on the orientation ratio in circumferentially-textured longitudinal recording media. Background on the magnetic anisotropy introduced by the circumferential texturing in cobalt-alloy longitudinal recording media; Methodology; Results and discussion.

Studies the gyromagnetic switching process in longitudinal thin film recording media by using numerical micromagnetics. Micromagnetic modeling; Simulated results of the dynamic recording process for media with different damping constants; Conclusion.

A micromagnetic Monte Carlo simulation is developed to study the thermal decay and erasure process for perpendicular recording media. The switching probability is calculated based on both the energy barrier analysis and the master equation. The results show that for current head media combination at 1 Tb/in², the ensure is severe for the neighboring tracks unless the bit-aspect ratio is increased. The magnetic write width for both side shielded (SS) and no side shield (NSS) head is about the same. The erase band for the SS write head is significantly smaller (20 nm less) than that for the NSS head, corresponding to 10 nm or 12% track pitch reduction. [ABSTRACT FROM AUTHOR]