Dynamic magnetic information storage or retrieval – General processing of a digital signal – Head amplifier circuit
Reexamination Certificate
2001-12-07
2004-03-02
Hudspeth, David (Department: 2651)
Dynamic magnetic information storage or retrieval
General processing of a digital signal
Head amplifier circuit
C360S125330, C360S123090, C360S324100, C360S324110, C360S324120
Reexamination Certificate
active
06700720
ABSTRACT:
TECHNICAL FIELD
The present invention is related to a method for ultrafast magnetization reversal with small applied magnetic fields. More particularly the invention relates to magnetic recording.
BACKGROUND OF THE INVENTION
Magnetization reversal is an elementary process underlying key technologies of our civilization such as electric transformation or magnetic recording. In conventional magnetization reversal as practiced today the reversing magnetic field is applied antiparallel to the magnetization direction. Therefore, the reversal speed is limited to a time scale which is at the nanosecond level.
Magnetic recording is an interdisciplinary field involving physics, material science, communications, and mechanical engineering. The physics of magnetic recording involves studying magnetic heads, recording media, and the process of transferring information between the heads and the medium.
Many magnetic recording systems, which are adaptable for recording and storing data, are known. Conventional systems employ a magnetizing pattern on the surface of a magnetic recording medium The magnetic medium has a magnetizing direction or a premagnetization whereby the pattern of magnetization is formed along the length of a single track, or a number of parallel tracks. The medium is in the form of a magnetic layer supported on a nonmagnetic substrate. Recording or writing takes place by causing relative motion between the medium and a recording transducer, also referred to as recording head. In general, the recording head is a ring-shaped electromagnet with a gap at the surface facing the medium. When the head is fed with a writing current representing the signal to be recorded, the fringing field from the gap magnetizes the medium, respectively. The recorded magnetization creates the above-mentioned pattern, that is in the simplest case a series of contiguous bar magnets. A “one bit” corresponds to a change in current polarity, while a “zero bit” corresponds to no change in polarity of the writing current. A moving disk is thus magnetized in the “+” direction for positive current and is magnetized in the “−” direction for negative current flow. In other words, the stored “ones” show up where reversals in magnetic direction occur on a disk and the “zeroes” reside between the “ones.”
A variety of magnetic media have been used for magnetic recording over the years. However, most modern magnetic media use a thin layer of ferromagnetic material supported by a non-magnetic substrate. The magnetic layer can be formed of magnetic particles in a polymer matrix. Alternatively, the layer can be a vacuum deposited metal or oxide film The use of a thin magnetic layer permits many possible configurations for the substrate. Magnetic media are differentiated into “hard” and “soft” media. Hard media require large applied fields to become permanently magnetized. Once magnetized, large fields are required to reverse the magnetization and erase the material. Such media, with large saturation and high coercivity are appropriate for such applications as computer data storage. Soft media, on the other hand, require relatively low fields to become magnetized. These materials are more appropriate for applications such as audio recording. The choice of the media influences the way the magnetization is recorded on the medium. This is because the direction of the recorded magnetization is strongly influenced by the magnetic anisotropy of the used medium. Thus, different techniques in recording exist, for example, longitudinal recording in which the magnetization direction is directed along the length of the track or perpendicular recording whereby the medium shows perpendicular anisotropy. Media with needle shaped particles oriented longitudinally tend to have a higher remanent magnetization in the longitudinal direction, and favor therefore longitudinal recording. This longitudinal orientation can then be supported by an appropriate head design, e.g. a ring head, which promotes longitudinal fields. Longitudinal recording is today's most applied and used technique. Nevertheless, a medium can also be constructed perpendicularly to the plane of a film Such media have a higher remanent magnetization in the perpendicular direction, and favor perpendicular recording. This perpendicular orientation can be supported by a head design, e.g. a single-pole head, which promotes perpendicular fields. Perpendicular recording media are generally recognized as supporting more stable high-density recording pattern than longitudinal media.
U.S. Pat. No. 5,268,799 is related to a magnetic recording and reproducing head that records a signal into and reproduces a signal from a magnetic recording medium having a perpendicularly magnetizable Mm The magnetic recording and reproducing head includes a magnetic sensing section comprising a slender needle of a soft magnetic material, and an exciting coil wound around the slender needle for magnetizing the slender needle to record a signal on the magnetic recording medium To reproduce the recorded signal high-frequency electric energy is applied to the magnetic sensing section to produce a reflected wave, and a change in the reflected wave caused by a leakage magnetic field produced by a signal recorded on the magnetic recording medium is detected as representing the recorded signal.
C. H. Back et al. describe in their article “Magnetization Reversal in Ultrashort Magnetic Field Pulses”, Physical Review Letters, Vol. 81, 3251 (1998), an experiment for studying magnetization reversal in perpendicularly magnetized Co/Pt films, whereby a short but strong magnetic field pulse is used. The applied magnetic field pulse is very strong and therefore not suitable for magnetic recording. Furthermore, a magnetic recording head is not able to generate such a strong, high energetic pulse.
Today's computers store data on magnetic disks in the form of binary digits or bits. Such a disk is rotating when the data are transmitted to the disk drive and processed in a corresponding time sequence of binary “one” and “zero” digits, or bits. Typical data rates today are about 30 MB/sec. This corresponds to magnetic-field pulses of 4 ns duration for recording. The current technologies apply antiparallel magnetic fields or magnetic-field pulses in order to reverse the magnetization direction.
Since the load of data which has to be stored increases dramatically, there is a need for faster operation in recording processes. Thus, the operating speed of the data storage systems is increasing. Today's systems show some drawbacks, e.g. the speed is physically limited, and are hence not suitable for new generations. With the conventional technology the reversal speed is in the nanosecond time scale. Therefore a much faster technology is required.
OBJECT OF THE INVENTION
It is an object of the present invention to overcome the disadvantages of the prior art.
It is another object of the present invention to provide a concept for high data rate recording.
It is still another object of the present invention to provide a method of performing ultrafast magnetization reversal.
It is a further object of the present invention to provide a method for ultrafast magnetic recording.
It is still a further object of the present invention to provide a device, a medium, and a system for ultrafast magnetic recording.
SUMMARY AND ADVANTAGES OF THE INVENTION
The objects of the invention are achieved by the features of the enclosed claims. Various modifications and improvements are contained in the dependent claims.
The underlying concept of the present invention concerns ultrafast magnetization reversal in an in-plane magnetized layer having a magnetization For achieving ultrafast magnetization reversal a small and short external magnetic field or field pulse is applied approximately perpendicular to the magnetization of the layer such that the magnetization precesses around the external magnetic field. The external magnetic field is only maintained until the precession suffices to effect the magnetization reversal
Allenspach Rolf
Back Christian Horst
Siegmann Hans-Christof Otto
Bracewell & Patterson L.L.P.
Figueroa Natalia
Hudspeth David
International Business Machines - Corporation
Martin Robert B.
LandOfFree
Ultrafast magnetization reversal does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Ultrafast magnetization reversal, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Ultrafast magnetization reversal will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3261894