Patents by Inventor Xizeng Shi

Xizeng Shi has filed for patents to protect the following inventions. This listing includes patent applications that are pending as well as patents that have already been granted by the United States Patent and Trademark Office (USPTO).

  • Patent number: 6697294
    Abstract: A reference cell circuit for a magnetic tunnel junction MRAM includes two magnetic tunnel junctions where one is always set to a low resistance state and the other is always set to a high resistance state. The two magnetic tunnel junctions are connected between two segments of a bit line. The reference cell also includes a digit line that crosses both of the bit line segments.
    Type: Grant
    Filed: January 22, 2002
    Date of Patent: February 24, 2004
    Assignee: Western Digital (Fremont), Inc.
    Inventors: Qiuqun Qi, Xizeng Shi, Matthew R. Gibbons
  • Patent number: 6687178
    Abstract: An MRAM storage device includes temperature dependent current sources that adjust their outputs as temperature varies. Temperature dependent current sources include one or more diodes connected to a transistor. As temperature varies so does the voltage drop across the diodes. In addition, the MRAM data storage device includes at least one digit line, at least one bit line, and at least one MRAM cell disposed proximate to a junction of a digit line and a bit line. Each end of each digit line is connected to temperature dependent current sources and current sinks. One end of each bit line is connected to a temperature dependent current source while the other end of each bit line is connected to a current sink. Two logic signals R and D are used to activate a write operation and determine the direction of the write current in the digit line.
    Type: Grant
    Filed: December 7, 2001
    Date of Patent: February 3, 2004
    Assignee: Western Digital (Fremont), Inc.
    Inventors: Qiuqun Qi, Xizeng Shi
  • Patent number: 6683763
    Abstract: A method and structure for providing a tunneling magnetoresistive (TMR) element is disclosed. The method and structure include providing a TMR layer that includes a first magnetic layer, a second magnetic layer and a first insulating layer disposed between the first magnetic layer and the second magnetic layer. The method and structure also include providing a first material and a protective layer. The first material allows electrical contact to be made to the tunneling magnetoresistive layer and is disposed above the tunneling magnetoresistive layer. The first material is capable of being undercut by an plasma etch without exposing a portion of the tunneling magnetoresistive layer under a remaining portion of the first material. The second protective layer covers a portion of the tunneling magnetoresistive sensor and a portion of the first material. In one aspect, the method and structure also include providing a second material disposed between the tunneling magnetoresistive layer and the first material.
    Type: Grant
    Filed: November 21, 2001
    Date of Patent: January 27, 2004
    Assignee: Western Digital (Fremont), Inc.
    Inventors: Hugh C. Hiner, Kyusik Sin, William Jensen, Xizeng Shi
  • Patent number: 6680863
    Abstract: A method and system for providing and using a magnetic memory including magnetic memory cells is disclosed. The method and system include providing a magnetic tunneling junction including a first ferromagnetic layer, a second ferromagnetic layer and an insulating layer between the first ferromagnetic layer and the second ferromagnetic layer. The magnetic memory cell is coupled to a merged word line and a bit line. The merged word line selects the magnetic memory cell during a reading and carries a write current for the magnetic memory cell during writing. The bit line provides current to the magnetic memory cell during the reading and the writing. The currents provided by the bit line and the merged word line during writing allow data to be written to the magnetic memory cell.
    Type: Grant
    Filed: July 9, 2002
    Date of Patent: January 20, 2004
    Assignee: Western Digital (Fremont), Inc.
    Inventors: Xizeng Shi, Qiuqun Qi
  • Patent number: 6639291
    Abstract: A tunneling barrier for a spin dependent tunneling (SDT) device is disclosed that includes a plurality of ferromagnetic particles. The presence of such particles in the tunneling barrier has been found to increase a magnetoresistance or &Dgr;R/R response, improving the signal and the signal to noise ratio. Such an increased &Dgr;R/R response also offers the possibility of decreasing an area of the tunnel barrier layer and/or increasing a thickness of the tunnel barrier layer. Decreasing the area of the tunnel barrier layer can afford improvements in resolution of devices such as MR sensors and increased density of devices such as of MRAM cells. Increasing the thickness of the tunnel barrier can afford improvements in manufacturing such as increased yield.
    Type: Grant
    Filed: February 6, 2002
    Date of Patent: October 28, 2003
    Assignee: Western Digital (Fremont), Inc.
    Inventors: Kyusik Sin, Shin Funada, Hugh Craig Hiner, Hua-Ching Tong, Xizeng Shi
  • Patent number: 6618223
    Abstract: An inductive write element is disclosed for use in a magnetic data recording system. The write element provides increased data rate and data density capabilities through improved magnetic flux flow through the element. The write element includes a magnetic yoke constructed of first and second magnetic poles. The first pole includes a pedestal constructed of a high magnetic moment (high Bsat) material, which is preferably FeRhN nanocrystalline films with lamination layers of CoZrCr. The second pole includes a thin inner layer of high Bsat material (also preferably FeRhN nanocrystalline films with lamination layers of CoZrCr), the remainder being constructed of a magnetic material capable of being electroplated, such as a Ni—Fe alloy. An electrically conductive coil passes through the yoke between the first and second poles to induce a magnetic flux in the yoke when an electrical current is caused to flow through the coil.
    Type: Grant
    Filed: July 18, 2000
    Date of Patent: September 9, 2003
    Assignee: Read-Rite Corporation
    Inventors: Yingjian Chen, Hua-Ching Tong, Lei Wang, Xizeng Shi
  • Patent number: 6552928
    Abstract: An MRAM data storage device has at least one digit line, at least one bit line, and at least one MRAM cell disposed proximate to a digit line and electrically connected to a bit line. Each end of each digit line is connected to a write current source and a write current sink. One end of each bit line is connected to a write current source and a read current source while the other end of each bit line is connected to a write current sink. Two logic signals R and D are used to determine the direction of the write current in the digit line, to select between the read current and the write current in the bit line. The state of the MRAM cell is read by detecting the voltage drop across the cell when a read current is applied.
    Type: Grant
    Filed: November 8, 2001
    Date of Patent: April 22, 2003
    Assignee: Read-Rite Corporation
    Inventors: Qiuqun Qi, Xizeng Shi
  • Patent number: 6512690
    Abstract: In the present invention, a magnetic random access memory (MRAM) cell includes a magnetic tunnel junction (MTJ) and a transistor. This memory cell provides a boosted output signal between different MTJ states stored. A method that is used by MRAM array for providing larger output voltage signal is also disclosed. The memory may comprise a plurality of such cells which are wired to form XY array. The source of the transistor is coupled to one end of the magnetic tunneling junction, while the drain of the transistor is coupled with an output for reading the magnetic memory cell. Another end of the magnetic tunneling junction is grounded. During reading, a constant voltage is applied to the gate of the transistor in selected memory cell. The drain of the transistor is connected to supply voltage via a load. The transistor functions both as switching element and amplifier to boost the output signal between different MTJ states. Either voltage or current at output can be detected to determine MTJ state.
    Type: Grant
    Filed: November 21, 2001
    Date of Patent: January 28, 2003
    Assignee: Read-Rite Corporation
    Inventors: Qiuqun (Kevin) Qi, Xizeng Shi
  • Patent number: 6468436
    Abstract: A system and method for providing a head for reading data is disclosed. The method and system include providing a magnetoresistive element and providing a flux guide having a high resistivity. The magnetoresistive element has an end. The flux guide also has an end. The end of the flux guide is adjacent to the end of the magnetoresistive element.
    Type: Grant
    Filed: July 12, 2000
    Date of Patent: October 22, 2002
    Assignee: Read-Rite Corporation
    Inventors: Xizeng Shi, Hua-Ching Tong, Ming Zhao, Francis Liu
  • Patent number: 6418048
    Abstract: A method and system for providing a top pinned spin-dependent tunneling sensor is disclosed. The method and system include providing a free layer, a tunneling barrier, a synthetic pinned layer and an antiferromagnetic layer. The free layer is ferromagnetic. The tunneling barrier is an insulator. The tunneling barrier is disposed between the free layer and the synthetic pinned layer. The synthetic pinned layer is ferromagnetic and includes a ferromagnetic top layer. The synthetic pinned layer is between the tunneling barrier and the antiferromagnetic layer. The ferromagnetic top layer acts as a seed layer for the antiferromagnetic layer.
    Type: Grant
    Filed: October 2, 2001
    Date of Patent: July 9, 2002
    Assignee: Read-Rite Corporation
    Inventors: Kyusik Sin, Shin Funada, Hugh C. Hiner, Xizeng Shi
  • Patent number: 6317297
    Abstract: A method and system for providing a magnetoresistive sensor is disclosed. The method and system include providing a first pinned layer, providing a first spacer layer above the first pinned layer, and providing a free layer above the first spacer layer. The method and system further include providing a second spacer layer above the free layer and providing a second pinned layer above the second spacer layer. The first pinned layer includes a first magnetic layer and a second magnetic layer separated by a first nonmagnetic layer. The first magnetic layer is antiferromagnetically coupled with the second magnetic layer. The second pinned layer includes a third magnetic layer and a fourth magnetic layer separated by a second nonmagnetic layer. The third magnetic layer is antiferromagnetically coupled with the fourth magnetic layer. The first pinned layer and the second pinned layer are pinned by a current carried by the magnetoresistive head during use.
    Type: Grant
    Filed: October 6, 1999
    Date of Patent: November 13, 2001
    Assignee: Read-Rite Corporation
    Inventors: Hua-Ching Tong, Xizeng Shi, Subrata Dey, Matthew Richard Gibbons
  • Patent number: 6137661
    Abstract: A system and method for providing a head for reading data is disclosed. The method and system include providing a magnetoresistive element and providing a flux guide having a high resistivity. The magnetoresistive element has an end. The flux guide also has an end. The end of the flux guide is adjacent to the end of the magnetoresistive element.
    Type: Grant
    Filed: October 19, 1998
    Date of Patent: October 24, 2000
    Assignee: Read-Rite Corporation
    Inventors: Xizeng Shi, Hua-Ching Tong, Ming Zhao, Francis Liu
  • Patent number: 5986978
    Abstract: A read/write head is structurally significantly less complicated than optical reading devices, requires minimal or no optical alignment, capable of writing at higher track densities, and has better control of the data and servo tracks than conventional magnetic heads. The head is also capable of using an available heat source and a relatively weak magnetic field, such as 300 Oersteds, to write data on a data storage medium. The combination of a magnetic read sensor with a near field magneto-optical (MO) write element creates a hybrid read/write head capable of high density recording with a high signal to noise ratio. The integration of the MO write element can be accomplished by various alternative or complementary methods. One method is to mount a heat source, such as a laser or light source on a slider with minimal or no additional optical components.
    Type: Grant
    Filed: January 12, 1998
    Date of Patent: November 16, 1999
    Assignee: Read-Rite Corporation
    Inventors: Robert E. Rottmayer, Charles C- K Cheng, Xizeng Shi, Lijun Tong, Hua-Ching Tong
  • Patent number: 5719730
    Abstract: A low fringe-field and narrow write-track magnetic read-write head. The low fringe-field and narrow write-track magnetic read-write head includes a first pole layer formed adjoining an insulator layer over a substrate. The first pole layer has a first air bearing surface which has a first edge adjoining and parallel with a first surface of the insulator layer. The low fringe-field and narrow write-track magnetic read-write head also includes a second pole layer separated from the first pole layer by the insulator layer. The second pole layer has a width no greater than about 20 microns and a width no greater than about 100 percent of the width of the first pole layer where the width of the second pole layer is contained within the width of the first pole layer. The second pole layer also has a second air bearing surface coplanar with the first air bearing surface.
    Type: Grant
    Filed: July 17, 1996
    Date of Patent: February 17, 1998
    Assignee: Headway Technologies, Inc.
    Inventors: Jei-Wei Chang, Kochan Ju, Yimin Guo, Xizeng Shi, Arthur Hungshin Tao
  • Patent number: 5684658
    Abstract: A method for forming a dual stripe magnetoresistive (DSMR) sensor element, and the dual stripe magnetoresistive (DSMR) sensor element formed through the method. To practice the method, there is formed upon a substrate a first magnetoresistive (MR) layer, where the first magnetoresistive (MR) layer has a first sensor region longitudinally magnetically biased in a first longitudinal bias direction through a patterned first longitudinal magnetic biasing layer. There is then formed a second magnetoresistive (MR) layer parallel with and separated from the first magnetoresistive (MR) layer by an insulator layer. The second magnetoresistive (MR) layer has a second sensor region longitudinally magnetically biased in a second longitudinal bias direction through a patterned second longitudinal magnetic biasing layer. The first longitudinal bias direction and the second longitudinal bias direction are substantially parallel. In addition, the first sensor region and the second sensor region are physically offset.
    Type: Grant
    Filed: October 7, 1996
    Date of Patent: November 4, 1997
    Assignee: Headway Technologies, Inc.
    Inventors: Xizeng Shi, Yimin Guo, Kochan Ju, Cherng-Chyi Han, Yimin Hsu, Jei-Wei Chang