Patents by Inventor Dimitar V. Dimitrov

Dimitar V. Dimitrov 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).

  • Publication number: 20120127787
    Abstract: A method of self-reference reading a spin-transfer torque memory unit includes applying a first read current through a magnetic tunnel junction data cell and forming a first bit line read voltage. The magnetic tunnel junction data cell has a first resistance state. Then the method includes applying a second read current thorough the magnetic tunnel junction data cell having the first resistance state. The first read current is less than the second read current. Then the first bit line read voltage is compared with the second bit line read voltage to determine whether the first resistance state of the magnetic tunnel junction data cell was a high resistance state or low resistance state.
    Type: Application
    Filed: January 12, 2012
    Publication date: May 24, 2012
    Applicant: SEAGATE TECHNOLOGY LLC
    Inventors: Yiran Chen, Hai Li, Hongyue Liu, Ran Wang, Dimitar V. Dimitrov
  • Publication number: 20120120718
    Abstract: An apparatus and associated method for a non-volatile memory cell, such as a multi-bit magnetic random access memory cell. In accordance with various embodiments, a magnetic tunnel junction (MTJ) has a ferromagnetic free layer with multiple magnetic domains that are each independently programmable to predetermined magnetizations. Those magnetizations can then be read as different logical states of the MTJ.
    Type: Application
    Filed: November 11, 2010
    Publication date: May 17, 2012
    Applicant: SEAGATE TECHNOLOGY LLC
    Inventors: Xiaohua Lou, Zheng Gao, Dimitar V. Dimitrov
  • Publication number: 20120106239
    Abstract: An apparatus and method for enhancing data writing and retention to a magnetic memory element, such as in a non-volatile data storage array. In accordance with various embodiments, a programmable memory element has a reference layer and a storage layer. The reference layer is provided with a fixed magnetic orientation. The storage layer is programmed to have a first region with a magnetic orientation antiparallel to said fixed magnetic orientation, and a second region with a magnetic orientation parallel to said fixed magnetic orientation. A thermal assist layer may be incorporated into the memory element to enhance localized heating of the storage layer to aid in the transition of the first region from parallel to antiparallel magnetic orientation during a write operation.
    Type: Application
    Filed: November 3, 2010
    Publication date: May 3, 2012
    Applicant: SEAGATE TECHNOLOGY LLC
    Inventors: Haiwen Xi, Yuankai Zheng, Xiaobin Wang, Dimitar V. Dimitrov, Pat J. Ryan
  • Publication number: 20120106241
    Abstract: A spin-transfer torque memory apparatus and self-reference read schemes are described. One method of self-reference reading a spin-transfer torque memory unit includes applying a first read current through a magnetic tunnel junction data cell and forming a first bit line read voltage, the magnetic tunnel junction data cell having a first resistance state and storing the first bit line read voltage in a first voltage storage device. Then applying a low resistance state polarized write current through the magnetic tunnel junction data cell, forming a low second resistance state magnetic tunnel junction data cell. A second read current is applied through the low second resistance state magnetic tunnel junction data cell to forming a second bit line read voltage. The second bit line read voltage is stored in a second voltage storage device.
    Type: Application
    Filed: January 12, 2012
    Publication date: May 3, 2012
    Applicant: SEAGATE TECHNOLOGY LLC
    Inventors: Hai Li, Yiran Chen, Hongyue Liu, Kang Yong Kim, Dimitar V. Dimitrov, Henry F. Huang
  • Patent number: 8169810
    Abstract: A magnetic tunnel junction cell includes a ferromagnetic reference layer, a ferromagnetic free layer, and a non-magnetic barrier layer separating the ferromagnetic reference layer from the ferromagnetic free layer. The magnetic tunnel junction cell has an asymmetric energy barrier for switching between a high resistance data state and a low resistance data state.
    Type: Grant
    Filed: July 6, 2009
    Date of Patent: May 1, 2012
    Assignee: Seagate Technology LLC
    Inventors: Wenzhong Zhu, Xiaohua Lou, Dimitar V. Dimitrov
  • Patent number: 8154914
    Abstract: A method and apparatus for using thermal preconditioning to write data to a non-volatile memory cell, such as a spin-torque transfer random access memory (STRAM) memory cell. In some embodiments, a logical state is written to an unconditioned non-volatile first memory cell associated with a first block address. Thermal preconditioning is concurrently applied to a non-volatile second memory cell associated with a second block address selected in response to the first block address.
    Type: Grant
    Filed: January 28, 2011
    Date of Patent: April 10, 2012
    Assignee: Seagate Technology LLC
    Inventors: Yiran Chen, Hai Li, Harry Hongyue Liu, Dimitar V. Dimitrov, Alan Xuguang Wang, Xiaobin Wang
  • Publication number: 20120081951
    Abstract: A method and apparatus for stray magnetic field compensation in a non-volatile memory cell, such as a spin-torque transfer random access memory (STRAM). In some embodiments, a first tunneling barrier is coupled to a reference structure that has a perpendicular anisotropy and a first magnetization direction. A recording structure that has a perpendicular anisotropy is coupled to the first tunneling barrier and a nonmagnetic spacer layer. A compensation layer that has a perpendicular anisotropy and a second magnetization direction in substantial opposition to the first magnetization direction is coupled to the nonmagnetic spacer layer. Further, the memory cell is programmable to a selected resistance state with application of a current to the recording structure.
    Type: Application
    Filed: December 12, 2011
    Publication date: April 5, 2012
    Applicant: SEAGATE TECHNOLOGY LLC
    Inventors: Dimitar V. Dimitrov, Olle Gunnar Heinonen, Dexin Wang, Haiwen Xi
  • Patent number: 8125746
    Abstract: A tunneling magneto-resistive reader includes a sensor stack separating a top magnetic shield from a bottom magnetic shield. The sensor stack includes a reference magnetic element having a reference magnetization orientation direction and a free magnetic element having a free magnetization orientation direction substantially perpendicular to the reference magnetization orientation direction. A non-magnetic spacer layer separates the reference magnetic element from the free magnetic element. A first side magnetic shield and a second side magnetic shield is disposed between the top magnetic shield from a bottom magnetic shield, and the sensor stack is between the first side magnetic shield and the second side magnetic shield. The first side magnetic shield and the second side magnetic shield electrically insulates the top magnetic shield from a bottom magnetic shield.
    Type: Grant
    Filed: July 13, 2009
    Date of Patent: February 28, 2012
    Assignee: Seagate Technology LLC
    Inventors: Dimitar V. Dimitrov, Zheng Gao, Wonjoon Jung, Paul Edward Anderson, Olle Gunnar Heinonen
  • Publication number: 20120039115
    Abstract: Spin-transfer torque memory includes a composite free magnetic element, a reference magnetic element having a magnetization orientation that is pinned in a reference direction, and an electrically insulating and non-magnetic tunneling barrier layer separating the composite free magnetic element from the magnetic reference element. The free magnetic element includes a hard magnetic layer exchanged coupled to a soft magnetic layer. The composite free magnetic element has a magnetization orientation that can change direction due to spin-torque transfer when a write current passes through the spin-transfer torque memory unit.
    Type: Application
    Filed: October 21, 2011
    Publication date: February 16, 2012
    Applicant: SEAGATE TECHNOLOGY LLC
    Inventors: Yuankai Zheng, Dimitar V. Dimitrov, Dexin Wang, Haiwen Xi, Kaizhong Gao, Olle Heinonen, Wenzhong Zhu
  • Patent number: 8116123
    Abstract: A spin-transfer torque memory apparatus and non-destructive self-reference read schemes are described. One method of self-reference reading a spin-transfer torque memory unit includes applying a first read current through a magnetic tunnel junction data cell and forming a first bit line read voltage and storing the first bit line read voltage in a first voltage storage device. The magnetic tunnel junction data cell has a first resistance state. Then the method includes applying a second read current thorough the magnetic tunnel junction data cell having the first resistance state and forming a second bit line read voltage and storing the second bit line read voltage in a second voltage storage device. The first read current is less than the second read current. Then the stored first bit line read voltage is compared with the stored second bit line read voltage to determine whether the first resistance state of the magnetic tunnel junction data cell was a high resistance state or low resistance state.
    Type: Grant
    Filed: June 27, 2008
    Date of Patent: February 14, 2012
    Assignee: Seagate Technology LLC
    Inventors: Yiran Chen, Hai Li, Hongyue Liu, Ran Wang, Dimitar V. Dimitrov
  • Patent number: 8116122
    Abstract: A spin-transfer torque memory apparatus and self-reference read schemes are described. One method of self-reference reading a spin-transfer torque memory unit includes applying a first read current through a magnetic tunnel junction data cell and forming a first bit line read voltage, the magnetic tunnel junction data cell having a first resistance state and storing the first bit line read voltage in a first voltage storage device. Then applying a low resistance state polarized write current through the magnetic tunnel junction data cell, forming a low second resistance state magnetic tunnel junction data cell. A second read current is applied through the low second resistance state magnetic tunnel junction data cell to forming a second bit line read voltage. The second bit line read voltage is stored in a second voltage storage device.
    Type: Grant
    Filed: June 27, 2008
    Date of Patent: February 14, 2012
    Assignee: Seagate Technology LLC
    Inventors: Hai Li, Yiran Chen, Hongyue Liu, Kang Yong Kim, Dimitar V. Dimitrov, Henry F. Huang
  • Publication number: 20120020148
    Abstract: A multi-bit spin torque magnetic element that has a ferromagnetic pinned layer having a pinned magnetization orientation, a non-magnetic layer, and a ferromagnetic free layer having a magnetization orientation switchable among at least four directions, the at least four directions being defined by a physical shape of the free layer. The magnetic element has at least four distinct resistance states. Magnetic elements with at least eight magnetization directions are also provided.
    Type: Application
    Filed: September 29, 2011
    Publication date: January 26, 2012
    Applicant: SEAGATE TECHNOLOGY LLC
    Inventor: Dimitar V. Dimitrov
  • Patent number: 8102691
    Abstract: Magnetic shift registers in which data writing and reading is accomplished by moving the magnetic domain walls by electric current. Various embodiments of domain wall nodes or anchors that stabilize a domain wall are provided. In some embodiments, the wall anchors are elements separate from the magnetic track. In other embodiments, the wall anchors are disturbances in the physical configuration of the magnetic track. In still other embodiments, the wall anchors are disturbances in the material of the magnetic track.
    Type: Grant
    Filed: June 24, 2008
    Date of Patent: January 24, 2012
    Assignee: Seagate Technology LLC
    Inventors: Haiwen Xi, Xiaobin Wang, Dimitar V. Dimitrov, Paul E. Anderson, Harry Liu, Song S. Xue, Andreas Roelofs, Markus Siegert
  • Patent number: 8098538
    Abstract: Method and apparatus for using a uni-directional write current to store different logic states in a non-volatile memory cell, such as a modified STRAM cell. In some embodiments, the memory cell has an unpinned ferromagnetic reference layer adjacent a cladded conductor, a ferromagnetic storage layer and a tunneling barrier between the reference layer and the storage layer. Passage of a current along the cladded conductor induces a selected magnetic orientation in the reference layer, which is transferred through the tunneling barrier for storage by the storage layer. Further, the orientation of the applying step is provided by a cladding layer adjacent a conductor along which a current is passed and the current induces a magnetic field in the cladding layer of the selected magnetic orientation.
    Type: Grant
    Filed: May 4, 2011
    Date of Patent: January 17, 2012
    Assignee: Seagate Technology LLC
    Inventors: Daniel Seymour Reed, Yong Lu, Song S. Xue, Dimitar V. Dimitrov, Paul E. Anderson
  • Patent number: 8091209
    Abstract: A magnetic sensor includes a sensor stack having a first magnetic portion, a second magnetic portion, and a barrier layer between the first magnetic portion and the second magnetic portion. The first magnetic portion and/or the second magnetic portion comprises a multilayer structure including a first magnetic layer having a positive magnetostriction adjacent to the barrier layer, a second magnetic layer, and an intermediate layer between the first magnetic layer and the second magnetic layer. The magnetic sensor exhibits a magnetoresistive ratio of at least about 62% with a resistance-area (RA) product of about 0.45 ?ยท?m2.
    Type: Grant
    Filed: October 3, 2007
    Date of Patent: January 10, 2012
    Assignee: Seagate Technology LLC
    Inventors: Zheng Gao, Dimitar V. Dimitrov, Song S. Xue
  • Patent number: 8089132
    Abstract: A magnetic memory unit includes a tunneling barrier separating a free magnetic element and a reference magnetic element. A first phonon glass electron crystal layer is disposed on a side opposing the tunneling barrier of either the free magnetic element or the reference magnetic element. A second phonon glass electron crystal layer also be disposed on a side opposing the tunneling barrier of either the free magnetic element or the reference magnetic element to provide a Peltier effect on the free magnetic element and the reference magnetic element.
    Type: Grant
    Filed: April 14, 2009
    Date of Patent: January 3, 2012
    Assignee: Seagate Technology LLC
    Inventors: Yuankai Zheng, Haiwen Xi, Dimitar V. Dimitrov, Dexin Wang
  • Patent number: 8077503
    Abstract: Electronic devices that include (i) a magnetization controlling structure; (ii) a tunnel barrier structure; and (iii) a magnetization controllable structure including: a first polarizing layer; and a first stabilizing layer, wherein the tunnel barrier structure is between the magnetization controlling structure and the magnetization controlling structure and the first polarizing layer is between the first stabilizing layer and the tunnel barrier structure, wherein the electronic device has two stable overall magnetic configurations, and wherein a first unipolar current applied to the electronic device will cause the orientation of the magnetization controlling structure to reverse its orientation and a second unipolar current applied to the electronic device will cause the magnetization controllable structure to switch its magnetization in order to obtain one of the two stable overall magnetic configurations, wherein the second unipolar current has an amplitude that is less than the first unipolar current.
    Type: Grant
    Filed: March 24, 2011
    Date of Patent: December 13, 2011
    Assignee: Seagate Technology LLC
    Inventors: Dimitar V. Dimitrov, Olle Gunnar Heinonen, Yiran Chen, Haiwen Xi, Xiaohua Lou
  • Patent number: 8077502
    Abstract: Electronic devices that include (i) a magnetization controlling structure; (ii) a tunnel barrier structure; and (iii) a magnetization controllable structure including: a first polarizing layer; and a first stabilizing layer, wherein the tunnel barrier structure is between the magnetization controlling structure and the magnetization controlling structure and the first polarizing layer is between the first stabilizing layer and the tunnel barrier structure, wherein the electronic device has two stable overall magnetic configurations, and wherein a first unipolar current applied to the electronic device will cause the orientation of the magnetization controlling structure to reverse its orientation and a second unipolar current applied to the electronic device will cause the magnetization controllable structure to switch its magnetization in order to obtain one of the two stable overall magnetic configurations, wherein the second unipolar current has an amplitude that is less than the first unipolar current.
    Type: Grant
    Filed: March 24, 2011
    Date of Patent: December 13, 2011
    Assignee: Seagate Technology LLC
    Inventors: Dimitar V. Dimitrov, Olle Gunnar Heinonen, Yiran Chen, Haiwen Xi, Xiaohua Lou
  • Publication number: 20110298068
    Abstract: A magnetic tunnel junction having a compsensation element is disclosed. The magnetic tunnel junction includes a reference element, and a compensation element having an opposite magnetization moment to a magnetization moment of the reference element. A free magnetic layer is between the reference element and the compensation element, and an electrically insulating and non-magnetic tunneling barrier layer separates the free magnetic layer from the reference element. The free magnetic layer includes Co100-X-YFeXBY wherein X is a value being greater than 30 and Y is a value being greater than 15.
    Type: Application
    Filed: August 16, 2011
    Publication date: December 8, 2011
    Applicant: SEAGATE TECHNOLOGY LLC.
    Inventors: Yuankai Zheng, Dimitar V. Dimitrov, Dexin Wang, Wei Tian, Xiaobin Wang, Xiaohua Lou
  • Patent number: 8054678
    Abstract: A method and apparatus for repairing a stuck-at defect condition in a non-volatile memory cell, such as a spin-torque transfer random access memory (STRAM). In some embodiments, a resistive sense element has a magnetic tunneling junction (MTJ) and a repair plane located adjacent to the resistive sense element. The repair plane injects a magnetic field in the MTJ to repair a stuck-at defect condition.
    Type: Grant
    Filed: October 7, 2010
    Date of Patent: November 8, 2011
    Assignee: Seagate Technology LLC
    Inventors: Alan Xuguang Wang, Xiaobin Wang, Dimitar V. Dimitrov, Hai Li, Haiwen Xi, Harry Hongyue Liu