International Business Machines Corporation

Bernell E Argyle

John Casimir Slonczewski

Lubomyr Taras Romankiw

Daniel A Nepela

Sol Krongelb

Hin P Lee

Dean A Herman, Jr

Bojan Petek

Thomas J Beaulieu

Thomas C Arnoldussen

Pieter Dekker

Jeffery Gregory McCord

Edward John Yarmchuk

Philip Louis Trouilloud

Michael E Scaman

Arnold Halperin

Shinji Takayama

Anthony Paul Praino

Mark E Re

Rudolf Schafer

An apparatus, system, and method for illuminating a lithographic mask or an object in a microscope is presented, whereby the output of a laser beam homogenizer is imaged on to a field such as the object plane for lithographic application or on to the rear focal plane of an epi illuminating objective lens as a source for wide field illumination at an object plane in a microscope (for application to magnified imaging of weak phase objects)., and the image of the output is dithered with respect to the field

Laser beam homogenizer

An optical apparatus and methods for efficiently determining the magnetization of a material at very high optical resolution are disclosed. Individual components of the magnetization may be determined. Components in the plane of the sample surface are imaged by illuminating the material obliquely with substantially parallel light of relatively high power and very well controlled uniformity and polarization, and using light scattered obliquely in a parallel beam in the opposite direction at the same angle as the angle of incidence to record an image. Reversing the illumination and observation directions allows subtraction of the two images and measurement of the magnetization in-plane. A second in-plane component orthogonal to the first, is obtained similarly after reorienting the plane of incidence 90 degrees. The third magnetization component,&mdash;perpendicular to the sample surface&mdash;, may be obtained using illumination at both angles of incidence and subtracting two images, each recorded when a light-polarization angle of offset from extinction, is reversed. All three components may thereby be imaged without recourse to modulating the sample magnetization as in previous methods. Magnetically 'hard' as well as 'soft' materials are measurable by these methods.

Apparatus and method for measuring magnetization of surfaces

An apparatus and corresponding method for detecting, locating, or defining a short in a thin-film module. The apparatus includes a mechanical fixture supporting the module. A current source provides a current pulse to the module which produces a magnetic field and heating nearby the short which turns on and off as the pulsed current in the short turns on and off. Polarized light is directed onto the module, with an intermediate element disposed between the module and the source of the polarized light. The intermediate element may be a stress birefringent coating (e.g., a polyimide insulating layer) disposed on the module and onto which the polarized light is directed. The sample is rotated 0 to 45 degrees to maximize the birefringent effect. Alternatively, the intermediate element may be a magneto-optical Faraday rotator. A microscope is used to observe the module, facilitating identification of a short by the twisting of the polarization of the light as the short expands and shrinks in response to the heating or in response to the localized magnetic field. The preferred rotator is a composite having a garnet substrate, an iron garnet film disposed on the substrate, and a thin aluminum mirror layer disposed on the iron garnet film. The apparatus and method of the present invention have several applications.

Method and apparatus for locating power plane shorts using polarized

A method and apparatus for conditioning a magnetic read/write head to substantially eliminate read-back pulse distortions associated with unfavorable magnetic domain patterns in the head stores the polarity of the last write current pulse of a write pulse train applied to the head-coils. This polarity is compared to a pre-determined reset current pulse polarity. If the last write current polarity is opposite to the reset current polarity, then a reset pulse, or a series of pulses, having the pre-determined reset polarity is applied to the head prior to performing a read operation with the head. The pre-determined reset polarity corresponds to the polarity that resets the head to the magnetic domain state most preferred for reading due to reduction of read-back distortion. The reset pulse, or pulse train, according to the present invention is of constant polarity. If the last write current pulse polarity is the same as the reset polarity, then no reset pulse is applied to the head. Prior to applying the reset pulse, the head is either re-positioned or, if not re-positioned, the reset pulse is applied to the head only when it is flying over a sector gap.

Electrical means to diminish read-back signal waveform distortion in

Magnetic thin film structures are disclosed including a laminate of a layer of nonmagnetic material sandwiched between first and second layers of magnetic material and at least one edge closure layer of magnetic material disposed on a side edge of the laminate with the edge closure layer being in magnetic contact with the first and second layers of magnetic material. The edge closure layer eliminates magnetic edge closure domains and magnetic edge-curling walls in the yoke and poletip regions, or in a fluxguide of a magnetic recording head to substantially eliminate Barkhausen noise and wall network instabilities. Multiple layer laminates are also disclosed having a plurality of nonmagnetic layers each of which are sandwiched between layers of magnetic material and wherein the laminate includes edge closure layers that contact all the magnetic layers. Several methods are disclosed for fabricating the laminate. In one class of technique, the side edges are deposited together with a top layer in a single plating operation. In an another embodiment, the side edge closure layers are separately plated. Another embodiment provides for a layer of antiferromagnetic material deposited between the nonmagnetic layer and one of the magnetic layers to provide additional anisotropy.

Magnetic thin film structures fabricated with edge closure layers

Magnetic thin film structures including a laminate of a layer of nonmagnetic material sandwiched between first and second layers of magnetic material and at least one edge closure layer of magnetic material disposed on a side edge of the laminate with the edge closure layer being in magnetic contact with the first and second layers of magnetic material. The edge closure layer eliminates magnetic edge closure domains and magnetic edge-curling walls in the yoke and poletip regions, or in a fluxguide of a magnetic recording head to substantially eliminate Barkhausen noise and wall network instabilities. Multiple layer laminates are also disclosed having a plurality of nonmagnetic layers each of which are sandwiched between layers of magnetic material and wherein the laminate includes edge closure layers that contact all the magnetic layers. Several methods are disclosed for fabricating the laminate. In one class of technique, the side edges are deposited together with a top layer in a single plating operation. In an another embodiment, the side edge closure layers are separately plated. Another embodiment provides for a layer of antiferromagnetic material deposited between the nonmagnetic layer and one of the magnetic layers to provide additional anisotropy.

Method of fabricating magnetic thin film structures with edge closure

Magnetic bubble domains are propagated in a magnetic medium in a desired direction using magnetic fields which have no spatial gradients. This is in contrast with conventional propagation techniques where magnetic overlays have to be used with applied magnetic fields in order to move domains. Depending upon the wall magnetization configurations in the domains, these domains are propagated by using, for example, a combination of a steady magnetic field and a magnetic field which varies with time, such as a pulse field or a sinusoidal field. This type of propagation is termed automotion. Bubbles which can automote are generated and detected in the magnetic medium using the principles of automotion. Embodiments are shown for representation of information using different types of bubbles, and in particular it is shown how to discriminate among bubble domains having wall configurations having a common winding number s. In a particular embodiment, a modulated bias field is superimposed on a steady magnetic field in the plane of the magnetic medium. Depending upon the direction of the in-plane magnetic field and upon the wall magnetization configuration of the bubbles, the bubbles can be made to move in different directions regardless of the directions of the modulated bias field.

Gradientless propulsion of magnetic bubble domains

Magnetic bubble domains are propagated in a magnetic medium in a desired direction using in-plane magnetic fields which are time varying but which have no spatial gradients. In applications such as information storage, the need for conventional propagation structures, such as offset conductor loops, patterned magnetic elements, and patterned ion implantation regions is reduced. Bubble domains having unwinding pairs of Bloch lines in their wall magnetization can be moved by applying appropriate in-plane magnetic fields, without the need for spatial gradients or variations in the magnetic field normal to the plane of the magnetic medium. The continuous movement of these bubble domains occurs by a cyclic process where the Bloch lines switch between two configurations, in an asymmetric way in response to the time varying in-plane field.

Gradientless propulsion of magnetic bubble domains using modulated

A technique for controllably providing state conversions between bubble domains having a common winding number S is described. In particular, controlled conversions between bubble domains having winding number S=1 is achieved by the application of spatially invariant, homogeneous magnetic fields. For the conversion of .sigma. bubbles (having two vertical Bloch lines) to .chi. bubbles (having no vertical Bloch lines), an in-plane field is not required and only a time varying perpendicular z-field is used. For conversion of a .chi..sub.+ bubble to a .chi..sub.- bubble, and vice versa, a time varying field pulse is applied, there being no requirement for an in-plane magnetic field. However, for the conversion of .chi. bubbles to .sigma. bubbles, an in-plane field is used simultaneously with a time varying z-field. For all controlled conversions, the applied magnetic fields do not have spatial gradients. The magnitudes of the applied magnetic fields and the rise and fall times of the z field are controlled within certain ranges in order to have controlled conversion of one state to another.

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Putnam Valley, NY, United States of America

Bernell E Argyle