Non-volatile magnetic memory device

• US 7,110,312 B2
• Filed: 10/19/2001
• Issued: 09/19/2006
• Est. Priority Date: 10/20/2000
• Status: Expired due to Fees

• Current Assignee: MicroMed Technology, Inc (MicroMed Cardiovascular, Inc.)
• Original Assignee: MicroMed Technology, Inc (MicroMed Cardiovascular, Inc.)
• Inventors: Stephenson, James, Carothers, Dan, Shipley, Bruce
• Primary Examiner(s): Yoha, Connie C.
• Application Number:
  US10/039,296
• Publication Number:
  US 20030007395A1
• Time in Patent Office: 1,796 Days
• Field of Search: 365/209, 365/145, 365/158, 365/171, 365/170
• US Class Current: 365/209
• CPC Class Codes: G11C 11/15 using multiple magnetic layers G11C11/155 takes precedence
• CPC Class Codes: G11C 11/1675 Writing or programming circuits or methods

Abstract

A non-volatile magnetic memory cell having a magnetic element with multiple segments which are not co-linear. Each of the segments is magnetized with a remnant magnetic field using a single write line. The segments can be magnetized in a first direction or a second direction, corresponding to first and second orientations of the memory cell. A sensor is provided to determine the direction in which the segments are magnetized and thereby the orientation of the cell. The segments are oriented such that the magnetic flux fields created by their respective remnant magnetic fields have a cumulative effect at a sensing region of the sensor. The cumulative effect allows a less sensitive sensor to be used than in known device. In various embodiments, the magnetic element can have a number of linear segments or a curved profile. In another embodiment, multiple magnetic elements are magnetized by a single write line. The multiple magnetic elements are arranged such that remnant magnetic field stored in them can be cumulatively sensed. In another embodiment, the magnetic element is arranged to be magnetized in a single general direction, but is shaped such that magnetic flux lines emanate from it in different directions. The different directions are arranged to direct flux lines through the sensing region of a sensor, which measures their cumulative effect.

Claims

1. A memory cell comprising:

(a) a non-linear magnetic element; and

(b) a single write line to store a remnant magnetic field in said magnetic element,

wherein said magnetic element has five or more segments that are not co-linear and wherein each of said segments stores a magnetic field.

2. The memory cell of claim 1 wherein said magnetic element has six segments.

3. A memory cell comprising:

(a) a non-linear magnetic element; and

(b) a single write line to store a remnant magnetic field in said magnetic element,

wherein said magnetic element is an incomplete toroid.

4. A memory cell comprising:

(a) first, second, and third magnetic elements;

(b) a sensor having a sensing region; and

(c) a single write line to store a remnant magnetic field in each of said magnetic elements,

wherein, when said memory cell is in a first orientation, the magnetic field in each of said magnetic elements has a first direction with respect to said sensing region, and when said memory cell is in a second orientation, the magnetic field in each of said magnetic elements has a second direction with respect to said sensing region, said write line including;

(i) a first segment aligned with said first element;

(ii) a second segment aligned with said second element; and

(iii) a third segment aligned with said third element,

wherein said second magnetic element has a trapezoidal cross-section and said first and third magnetic elements positioned adjacent to said second magnetic element are shaped to correspond to the shape of the second magnetic element.

5. A memory cell comprising:

(a) a magnetic element having a notched section;

(b) a single write line adjacent to said magnetic element to store a remnant magnetic field in said magnetic element, said magnetic field having a first orientation or a second orientation; and

(c) a sensor having a sensing region to detect the orientation of said magnetic field,

wherein said notched section is defined by two or more sides of said magnetic element adjacent to said sensing region, said notched section having a trapezoidal shape defined by three sides of said magnetic element.

6. The memory cell of claim 5 wherein said magnetic field stored in said magnetic element creates a magnetic flux field passing through said sensing region.

7. The memory cell of claim 6 wherein said magnetic flux field has magnetic flux lines that emanate from each of said sides.

8. The memory cell of claim 7 wherein at least some of said magnetic flux lines emanate from said sides at an angle corresponding to the permeability gradient between said magnetic element and surrounding materials.