Non-volatile magnetic random access memory

An improved non-volatile magnetic random access memory of the type having an array of unit cells, each cell having a Hall-effect sensor comprised of a rectangular shape of semiconductor material and a thin-film magnetic element of selected dimension, the magnetic element having a length greater than width and being made of material having an in-plane uniaxial anisotropy and in-plane bipolar remanent magnetization states along the length, the magnetic element being positioned with one end near the center of the Hall-effect sensor, means for selectively conducting a sensing current through the Hall-effect sensor from one side to an opposite side of the rectangular shape in a direction perpendicular to the length of the thin-film magnetic element, thereby producing a differential in electrical potentials on sides of the rectangular shape that are perpendicular to the sides of the semiconductor material through which current is conducted, and means for amplifying the differential in electrical potentials, whereby a signal is produced the polarity of which corresponds to the state of the bipolar remanent magnetization of the thin-film magnetic element along its length, each cell further having a conductor perpendicular to and overlaying the length of the thin-film magnetic element and means for applying a current through the conductor with a selected polarity for storing a binary digit 1 or 0 in the thin-film magnetic element, thereby setting the bipolar remanent magnetization state of the thin-film magnetic element to a selected state representative of a binary digit of 1 or 0;

• the improvement comprising:
• a Hall-effect sensor made of a layer of semiconductor material separated from a substrate by a buffering layer of material;
• wherein said layer of semiconductor material comprises InAs grown by molecular beam epitaxy.

An improved non-volatile magnetic random access memory of the type having an array of unit cells, each cell having a Hall-effect sensor comprised of a rectangular shape of semiconductor material and a thin-film magnetic element of selected dimension, the magnetic element having a length greater than width and being made of material having an in-plane uniaxial anisotropy and in-plane bipolar remanent magnetization states along the length, the magnetic element being positioned with one end near the center of the Hall-effect sensor, means for selectively conducting a sensing current through the Hall-effect sensor from one side to an opposite side of the rectangular shape in a direction perpendicular to the length of the thin-film magnetic element, thereby producing a differential in electrical potentials on sides of the rectangular shape that are perpendicular to the sides of the semiconductor material through which current is conducted, and means for amplifying the differential in electrical potentials, whereby a signal is produced the polarity of which corresponds to the state of the bipolar remanent magnetization of the thin-film magnetic element along its length, each cell further having a conductor perpendicular to and overlaying the length of the thin-film magnetic element and means for applying a current through the conductor with a selected polarity for storing a binary digit 1 or 0 in the thin-film magnetic element, thereby setting the bipolar remanent magnetization state of the thin-film magnetic element to a selected state representative of a binary digit of 1 or 0;

• wherein said array is a rectangular array having a plurality of columns of said unit cells and a plurality of rows of said unit cells, and wherein said differential in electrical potentials on the sides of said rectangular shape of semiconductor material of each Hall-effect sensor in a column is connected in series with all other differentials of electrical potentials of Hall-effect sensors of the same column, and said series connection of differentials in electrical potentials for a single column is connected to said amplifying means while said means for selectively conducting a sensing current is conducting sensing current in only one unit cell of said column connected in series;
• said array including a single data bit output terminal for all columns of said array, and wherein said means for selectively conducting a sensing current through said semiconductor material from one side to an opposite side of every unit cell in a row of said rectangular array is comprised of a conductive path through each unit cell of a row, means for on and off switching control of current through said each conductive path to select a row of said array for read out, and means for selectively enabling differentials in electrical potentials in series of a single column to be amplified and presented at said single data bit output terminal;
• and
• wherein said means for selecting the polarity of current through said conductor perpendicular to said length of said thin-film magnetic element of each unit cell of said array comprises a source of current, switching means for each column of unit cells for selectively turning on said current source for a selected column of unit cells and selecting the polarity of said current to said selected column of unit cells, and a separate switch for selectively connecting said current source to a unit cell of a selected row in said selected column;
• the improvement comprising:
• conductive means associated with each said path of each said Hall-effect sensor in said array for isolating each such sensor from all other sensors in said array.

An improved non-volatile magnetic random access memory of the type having an array of unit cells, each cell having a Hall-effect sensor comprised of a rectangular shape of semiconductor material and a thin-film magnetic element of selected dimension, the magnetic element having a length greater than width and being made of material having an in-plane uniaxial anisotropy and in-plane bipolar remanent magnetization states along the length, the magnetic element being positioned with one end near the center of the Hall-effect sensor, means for selectively conducting a sensing current through the Hall-effect sensor from one side to an opposite side of the rectangular shape in a direction perpendicular to the length of the thin-film magnetic element, thereby producing a differential in electrical potentials on sides of the rectangular shape that are perpendicular to the sides of the semiconductor material through which current is conducted, and means for amplifying the differential in electrical potentials, whereby a signal is produced the polarity of which corresponds to the state of the bipolar remanent magnetization of the thin-film magnetic element along its length, each cell further having a conductor perpendicular to and overlaying the length of the thin-film magnetic element and means for applying a current through the conductor with a selected polarity for storing a binary digit 1 or 0 in the thin-film magnetic element, thereby setting the bipolar remanent magnetization state of the thin-film magnetic element to a selected state representative of a binary digit of 1 or 0;

• the improvement comprising:
• means associated with said magnetic element overlying conducting for reducing the current through said conductor required for storing a binary digit in said magnetic element;
• wherein said current-reducing means comprises a picture-frame-like conductor.

An improved non-volatile magnetic random access memory of the type having an array of unit cells, each cell having a Hall-effect sensor comprised of a rectangular shape of semiconductor material and a thin-film magnetic element of selected dimension, the magnetic element having a length greater than width and being made of material having an in-plane uniaxial anisotropy and in-plane bipolar remanent magnetization states along the length, the magnetic element being positioned with one end near the center of the Hall-effect sensor, means for selectively conducting a sensing current through the Hall-effect sensor from one side to an opposite side of the rectangular shape in a direction perpendicular to the length of the thin-film magnetic element, thereby producing a differential in electrical potentials on sides of the rectangular shape that are perpendicular to the sides of the semiconductor material through which current is conducted, and means for amplifying the differential in electrical potentials, whereby a signal is produced the polarity of which corresponds to the state of the bipolar remanent magnetization of the thin-film magnetic element along its length, each cell further having a conductor perpendicular to and overlaying the length of the thin-film magnetic element and means for applying a current through the conductor with a selected polarity for storing a binary digit 1 or 0 in the thin-film magnetic element, thereby setting the bipolar remanent magnetization state of the thin-film magnetic element to a selected state representative of a binary digit of 1 or 0;

• the improvement comprising:
• means associated with said magnetic element overlying conductor for reducing the current through said conductor required for storing a binary digit in said magnetic element;
• wherein said current-reducing means comprises top and bottom conductors interconnected by vias and forming a multiple-turn coil around said magnetic element.

An improved non-volatile magnetic random access memory of the type having an array of unit cells, each cell having a Hall-effect sensor comprised of a rectangular shape of semiconductor material and a thin-film magnetic element of selected dimension, the magnetic element having a length greater than width and being made of material having an in-plane uniaxial anisotropy and in-plane bipolar remanent magnetization states along the length, the magnetic element being positioned with one end near the center of the Hall-effect sensor, means for selectively conducting a sensing current through the Hall-effect sensor from one side to an opposite side of the rectangular shape in a direction perpendicular to the length of the thin-film magnetic element, thereby producing a differential in electrical potentials on sides of the rectangular shape that are perpendicular to the sides of the semiconductor material through which current is conducted, and means for amplifying the differential in electrical potentials, whereby a signal is produced the polarity of which corresponds to the state of the bipolar remanent magnetization of the thin-film magnetic element along its length, each cell further having a conductor perpendicular to and overlaying the length of the thin-film magnetic element and means for applying a current through the conductor with a selected polarity for storing a binary digit 1 or 0 in the thin-film magnetic element, thereby setting the bipolar remanent magnetization state of the thin-film magnetic element to a selected state representative of a binary digit of 1 or 0;

• the improvement comprising:
• a semiconductor material that is GaAs;
• wherein each such unit cell has associated with it at least one switching transistor for selectively storing a binary digit in said magnetic element and at least switching transistor for selectively sensing the state of said binary digit;
• each such transistor comprising GaAs.

An improved non-volatile magnetic random access memory of the type having an array of unit cells, each cell having a Hall-effect sensor comprised of a rectangular shape of semiconductor material on a thin-film magnetic element of selected dimension, the magnetic element having a length greater than width and being made of material having an in-plane uniaxial anisotropy and in-plane bipolar remanent magnetization states along the length, the magnetic element being positioned with one end near the center of the Hall-effect sensor, means for selectively conducting a sensing current through the Hall-effect sensor from one side to an opposite side of the rectangular shape in a direction perpendicular to the length of the thin-film magnetic element, thereby producing a differential in electrical potentials on sides of the rectangular shape that are perpendicular to the sides of the semiconductor material through which current is conducted, and means for amplifying the differential in electrical potentials, whereby a signal is produced the polarity of which corresponds to the state of the bipolar remanent magnetization of the thin-film magnetic element along its length, each cell further having a conductor perpendicular to and overlaying the length of the thin-film magnetic element and means for applying a current through the conductor with a selected polarity for storing a binary digit 1 or 0 in the thin-film magnetic element, thereby setting the bipolar remanent magnetization state of the thin-film magnetic element to a selected state representative of a binary digit of 1 or 0;

• the improvement comprising:
• the improvement wherein said thin film magnetic element comprises a material taken from the group consisting of NiFe, .gamma.-Fe.sub.2 O.sub.3, CoPt, CoPt0 and other alloys of cobalt;
• wherein said Hall-effect sensor is made of semiconductor material separated from a substrate by a buffering layer;
• wherein said buffering layer comprises material taken from the group consisting of GaAs, AlAs, AlGaAs and InAlAs.