Differential magnetoresistive sensor for vertical recording

Claim 1

A sensor for reading binary data stored on a magnetic surface in the form of recorded flux field transitions comprising: a pair of thin film mutually-biased magnetoresistive strips, corresponding ends of which are interconnected to define first and second terminals, one of which is adapted to be connected to a constant current source, said strips being spaced apart in parallel relationship so that a substantially different field is sensed by each of said strips, said strips having substantially the same resistance value R, whereby the magnetoresistive strips are connected such that the current I supplied from said source splits substantially equally between said strips to cause said strips to be biased in opposite directions and at the same corresponding point in the linear region of the respective magnetoresistive curves for said strips; and means for obtaining an output signal V from said sensor in response to each said strip sensing magnetic flux components that have been stored on a magnetic surface and that are substantially parallel to the respective bias fields, said signal V being (1) constant when said flux components are in the same direction and of substantially the same value which results in a zero net change in the effective resistance between said terminals, and (2) variable in proportion to the algebraic difference in the respective values of said flux components to produce a unimodal signal.

Claim 8

A method of reading vertically recorded data stored on a magnetic surface to provide a unimodal pulse type signal at each flux field transition by means of a two terminal magnetoresistive sensing device having a pair of thin film magnetoresistive strips being spaced apart so that a substantially different field is sensed by each of said strips, said strips being disposed parallel to each other in a plane parallel to said transitions and connected between said two terminals, said method comprising the steps of: (1) supplying a constant current to one terminal of said device to cause current to flow through each said strip to said second terminal in equal amounts such that said strips are magnetically biased in opposite directions to corresponding points on their respective magnetoresistive curves; and (2) simultaneously moving said device parallel to said surface to vary the resistance of each said strip in accordance with the direction and value of vertical flux components which are sensed by each said strip whereby the net change in resistance between said first and second terminal is zero except when scanning a transition where the vertical flux components change direction and the effects of said oppositely directed vertical flux components on each said strip are differentially summed internally of said device to create a unimodal type voltage signal at said first terminal.

Claim 9

A method of reading vertically recorded data stored on a magnetic surface to provide a unimodal pulse type signal at each flux field transition by means of a two terminal magnetoresistive sensing device having a pair of thin film magnetoresistive strips being spaced apart so that a substantially different field is sensed by each of said strips, said strips being disposed parallel to each other in a plane parallel to said transitions and connected between said two terminals, said method comprising the steps of: (1) supplying a constant current to one terminal of said device to cause current to flow through each said strip to said second terminal in equal amounts such that said strips are magnetically biased in opposite directions to corresponding points on their respective magnetoresistive curves; and (2) simultaneously moving said device parallel to said surface to vary the resistance of each said strip in accordance with the direction and value of vertical flux components which are sensed by each said strip whereby the net change in resistance between said first and second terminal is zero except when scanning a transition where the vertical flux components change direction and the effects of said oppositely directed vertical flux components on each said strip are differentially summed internally of said device to create a unimodal type voltage signal at said first terminal.

Claim 10

A method of sensing vertically recorded binary data stored in the form of fluid field transistions on a magnetic surface, said method comprising the steps of: (1) oppositely biasing a pair of magnetoresistive strips which are (a) connected in parallel between first and second terminals, and (b) spaced apart physically a distance which is relatively small compared to the recording density of said binary data on said magnetic surface so that a substantially different field is sensed by each of said strips, said biasing step including supplying to said first terminal a current I to cause a current of I/2 to flow in each strip simultaneously whereby said strips are biased in opposite directions to corresponding points on their respective magnetoresistive curves; (2) positioning said strips in flux sensing relationship with said magnetic surface with the plane of said strips parallel to said flux transitions defined by the vertical components of magnetic flux emanating from said surface in opposite directions; (3) moving said strips parallel to said surface to scan said transitions; and (4) simultaneously monitoring the voltage at said first terminal to provide an indication of the value of said stored binary data represented by each transition in accordance with the polarity of the unimodal voltage signal developed at said first terminal.

Claim 11

A method of sensing vertically recorded binary data stored in the form of fluid field transistions on a magnetic surface, said method comprising the steps of: (1) oppositely biasing a pair of magnetoresistive strips which are (a) connected in parallel between first and second terminals, and (b) spaced apart physically a distance which is relatively small compared to the recording density of said binary data on said magnetic surface so that a substantially different field is sensed by each of said strips, said biasing step including supplying to said first terminal a current I to cause a current of I/2 to flow in each strip simultaneously whereby said strips are biased in opposite directions to corresponding points on their respective magnetoresistive curves; (2) positioning said strips in flux sensing relationship with said magnetic surface with the plane of said strips parallel to said flux transitions defined by the vertical components of magnetic flux emanating from said surface in opposite directions; (3) moving said strips parallel to said surface to scan said transitions; and (4) simultaneously monitoring the voltage at said first terminal to provide an indication of the value of said stored binary data represented by each transition in accordance with the polarity of the unimodal voltage signal developed at said first terminal.