Patents by Inventor Kenchi Ito
Kenchi Ito 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).
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Publication number: 20110222333Abstract: Provided is a highly-integrated magnetic memory which employs applied spin torque magnetization reversal and does not require the switching of the current direction at the time of rewrite. The magnetic memory includes a memory cell in which a fixed layer made of a ferromagnetic material, a nonmagnetic layer, a recording layer made of a ferromagnetic material, a nonmagnetic layer, and a magnetization rotation assist layer made of a ferromagnetic material are stacked one on top of another. The magnetic memory performs recording by making the magnetization direction of the recording layer substantially parallel or substantially antiparallel to the magnetization direction of the fixed layer.Type: ApplicationFiled: May 26, 2009Publication date: September 15, 2011Inventor: Kenchi Ito
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Patent number: 7872906Abstract: A memory for which writing is conducted by using a unidirectional write current. Currents which differ in current pulse width are applied to a magnetoresistance element in a film thickness direction of the magnetoresistance element consisting of a first ferromagnetic layer having a fixed magnetization direction, a second ferromagnetic layer having a variable magnetization direction, a third ferromagnetic layer having a variable magnetization direction, a first non-magnetic layer located between the first ferromagnetic layer and the second ferromagnetic layer, and a second non-magnetic layer located between the second ferromagnetic layer and the third ferromagnetic layer, to reverse a magnetization direction of either the second ferromagnetic layer or the third ferromagnetic layer by using a spin-transfer torque.Type: GrantFiled: December 18, 2008Date of Patent: January 18, 2011Assignee: Hitachi, Ltd.Inventors: Katsuya Miura, Jun Hayakawa, Hiromasa Takahashi, Kenchi Ito
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Patent number: 7787290Abstract: In MRAM using a spin-transfer torque switching, a sufficient writing operation with a small memory cell is realized, and a reading current is enlarged while a reading disturbance is suppressed. In the case where the free layer of the tunnel magneto-resistance element is located on the side of the bit line, using a PMOS transistor, and in the case where the fixed layer of the tunnel magneto-resistance element is located on the side of the bit line, using an NMOS transistor, an anti-parallel writing in a source grounding operation is performed. The reading and writing operation margin is improved by performing a reading operation in an anti-parallel writing direction.Type: GrantFiled: August 21, 2009Date of Patent: August 31, 2010Assignee: Hitachi, Ltd.Inventors: Riichiro Takemura, Takayuki Kawahara, Kenchi Ito, Hiromasa Takahashi
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Patent number: 7778068Abstract: In a memory using spin transfer torque, state of the spin is made unstable by applying a weak pulse before rewriting to reduce rewrite current. Reading of high-speed operation is performed with current in a regime where the current becomes non-linearly increases corresponding to the pulse width to suppress disturb. Further, fluctuation of respective memory cells is suppressed by a driving method setting the amount of spin constant by bit line charge to suppress read disturb.Type: GrantFiled: August 21, 2009Date of Patent: August 17, 2010Assignee: Hitachi, Ltd.Inventors: Takayuki Kawahara, Riichiro Takemura, Kenchi Ito, Hiromasa Takahashi
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Patent number: 7764538Abstract: A magnetic random access memory which employs spin torque magnetization reversal having a small write current value is applied. The memory includes: a switching element the conduction of which is controlled by a gate electrode, and three magnetoresistance effect elements connected to the switching element in series. Each magnetoresistance effect element may be a TMR element or a GMR element that includes a multilayered film composed of a fixed layer, a non-magnetic layer and a free layer. The central element serves as a storage element. The magnetoresistance effect elements are manufactured such that an absolute value of current necessary for changing a magnetization direction of at least one of the magnetoresistance effect elements located at both ends is larger than an absolute value of current necessary for changing a magnetization direction of the central magnetoresistance effect element.Type: GrantFiled: December 12, 2008Date of Patent: July 27, 2010Assignee: Hitachi, Ltd.Inventor: Kenchi Ito
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Patent number: 7755932Abstract: An object of the present invention corrects fluctuation of a writing current between cells in a magnetic random access memory using spin torque magnetization reversal. The present invention includes a magneto-resistive effect element that is disposed between a bit line and a word line, a first variable resistance element that is connected to one end of the bit line, a second variable resistance element that is connected to the other end of the bit line, a first voltage applying unit that applies voltage to the first variable resistance element, and a second voltage applying unit that applies voltage to the second variable resistance element, when a writing operation is performed, an offset magnetic field is applied to a free layer of the magneto-resistive effect element by flowing a variable current between the first voltage applying unit and the second voltage applying unit based on a predetermined resistance value.Type: GrantFiled: December 19, 2008Date of Patent: July 13, 2010Assignee: Hitachi, Ltd.Inventors: Kenchi Ito, Jun Hayakawa, Katsuya Miura
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Patent number: 7738286Abstract: A magnetic memory device comprises a magnetic tunnel junction (MTJ) connecting to a bit line to a sense line through an isolation transistor. The MTJ includes a ferromagnetic layer having a magnetic hard axis. An assist current line overlies the bit line and is insulated from the bit line. The MTJ is switchable between a first, relatively high resistance state and a second, relatively low resistance state. The assist current line applies a magnetic field along the magnetic hard axis in the ferromagnetic layer, independently of current flow through the MTJ for assisting switching of the MTJ between the first and second states.Type: GrantFiled: December 14, 2006Date of Patent: June 15, 2010Assignees: Hitachi, Ltd., Centre National de la Recherche Scientifique, Universite Paris Sud XIInventors: Kenchi Ito, Hiromasa Takahashi, Takayuki Kawahara, Riichiro Takemura, Thibault Devolder, Paul Crozat, Joo-von Kim, Claude Chappert
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Patent number: 7675836Abstract: For providing a recording/reproducing apparatus, for recording/reproducing information through conduction of electricity upon contact of a probe, having large recording density and a large transfer speed, but less in deterioration of a probe chips thereof, and being long in the lifetime thereof, within the recording/reproducing apparatus, a multi-chip is formed, disposing probe chips in large numbers thereof at a tip of a cantilever, while the cantilever is of a double-sided beam type, and the multi-chip is disposed at a center of the beam, wherein recording/reproducing portions of the multi-chip are disposed to correspond to recording dots one by one, and the multi-chip forming surface is moved up and down in parallel with the surface of a recording medium, due to suction force, so as to bring it to be in contact with the recording dots, and electricity is conducted after the contact thereof, thereby conducting the recording, in the structure; wherein, since a large amount of data can be read/written at oneType: GrantFiled: June 30, 2005Date of Patent: March 9, 2010Assignee: Hitachi, Ltd.Inventors: Mieko Ishii, Takeshi Harada, Youichi Inoue, Kenchi Ito
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Publication number: 20090310399Abstract: In a memory using spin transfer torque, state of the spin is made unstable by applying a weak pulse before rewriting to reduce rewrite current. Reading of high-speed operation is performed with current in a regime where the current becomes non-linearly increases corresponding to the pulse width to suppress disturb. Further, fluctuation of respective memory cells is suppressed by a driving method setting the amount of spin constant by bit line charge to suppress read disturb.Type: ApplicationFiled: August 21, 2009Publication date: December 17, 2009Applicant: HITACHI, LTD.Inventors: Takayuki Kawahara, Riichiro Takemura, Kenchi ITO, Hiromasa Takahashi
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Publication number: 20090310400Abstract: In MRAM using a spin-transfer torque switching, a sufficient writing operation with a small memory cell is realized, and a reading current is enlarged while a reading disturbance is suppressed. In the case where the free layer of the tunnel magneto-resistance element is located on the side of the bit line, using a PMOS transistor, and in the case where the fixed layer of the tunnel magneto-resistance element is located on the side of the bit line, using an NMOS transistor, an anti-parallel writing in a source grounding operation is performed. The reading and writing operation margin is improved by performing a reading operation in an anti-parallel writing direction.Type: ApplicationFiled: August 21, 2009Publication date: December 17, 2009Applicant: HITACHI, LTD.Inventors: Riichiro Takemura, Takayuki Kawahara, Kenchi Ito, Hiromasa Takahashi
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Patent number: 7596014Abstract: In a memory using spin transfer torque, state of the spin is made unstable by applying a weak pulse before rewriting to reduce rewrite current. Reading of high-speed operation is performed with current in a regime where the current becomes non-linearly increases corresponding to the pulse width to suppress disturb. Further, fluctuation of respective memory cells is suppressed by a driving method setting the amount of spin constant by bit line charge to suppress read disturb.Type: GrantFiled: April 17, 2007Date of Patent: September 29, 2009Assignee: Hitachi, Ltd.Inventors: Takayuki Kawahara, Riichiro Takemura, Kenchi Ito, Hiromasa Takahashi
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Patent number: 7593253Abstract: In MRAM using a spin-transfer torque switching, a sufficient writing operation with a small memory cell is realized, and a reading current is enlarged while a reading disturbance is suppressed. In the case where the free layer of the tunnel magneto-resistance element is located on the side of the bit line, using a PMOS transistor, and in the case where the fixed layer of the tunnel magneto-resistance element is located on the side of the bit line, using an NMOS transistor, an anti-parallel writing in a source grounding operation is performed. The reading and writing operation margin is improved by performing a reading operation in an anti-parallel writing direction.Type: GrantFiled: April 17, 2007Date of Patent: September 22, 2009Assignee: Hitachi, Ltd.Inventors: Riichiro Takemura, Takayuki Kawahara, Kenchi Ito, Hiromasa Takahashi
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Publication number: 20090180312Abstract: A memory for which writing is conducted by using a unidirectional write current. Currents which differ in current pulse width are applied to a magnetoresistance element in a film thickness direction of the magnetoresistance element consisting of a first ferromagnetic layer having a fixed magnetization direction, a second ferromagnetic layer having a variable magnetization direction, a third ferromagnetic layer having a variable magnetization direction, a first non-magnetic layer located between the first ferromagnetic layer and the second ferromagnetic layer, and a second non-magnetic layer located between the second ferromagnetic layer and the third ferromagnetic layer, to reverse a magnetization direction of either the second ferromagnetic layer or the third ferromagnetic layer by using a spin-transfer torque.Type: ApplicationFiled: December 18, 2008Publication date: July 16, 2009Inventors: Katsuya MIURA, Jun Hayakawa, Hiromasa Takahashi, Kenchi Ito
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Publication number: 20090168501Abstract: Provided is a magnetic random access memory employing spin torque magnetization reversal having a small write current value is applied. The memory includes: a switching element the conduction of which is controlled by a gate electrode, and three magnetoresistance effect elements connected to the switching element in series. Each magnetoresistance effect element may be a TMR element or a GMR element that includes a multilayered film composed of a fixed layer, a non-magnetic layer and a free layer. The central element serves as a storage element. The magnetoresistance effect elements are manufactured such that an absolute value of current necessary for changing a magnetization direction of at least one of the magnetoresistance effect elements located at both ends is larger than an absolute value of current necessary for changing a magnetization direction of the central magnetoresistance effect element.Type: ApplicationFiled: December 12, 2008Publication date: July 2, 2009Inventor: Kenchi Ito
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Patent number: 7554834Abstract: A conduction control device comprises a first ferromagnetic region having relatively high coercivity, a second ferromagnetic region having relatively low coercivity and a junction region disposed between the first and second ferromagnetic regions. The device also comprises a gate for applying a field to the junction region so as to control charge carrier density within the junction region.Type: GrantFiled: March 23, 2006Date of Patent: June 30, 2009Assignee: Hitachi, Ltd.Inventors: Jörg Wunderlich, Kenchi Ito
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Publication number: 20090161414Abstract: An object of the present invention corrects fluctuation of a writing current between cells in a magnetic random access memory using spin torque magnetization reversal. The present invention includes a magneto-resistive effect element that is disposed between a bit line and a word line, a first variable resistance element that is connected to one end of the bit line, a second variable resistance element that is connected to the other end of the bit line, a first voltage applying unit that applies voltage to the first variable resistance element, and a second voltage applying unit that applies voltage to the second variable resistance element, when a writing operation is performed, an offset magnetic field is applied to a free layer of the magneto-resistive effect element by flowing a variable current between the first voltage applying unit and the second voltage applying unit based on a predetermined resistance value.Type: ApplicationFiled: December 19, 2008Publication date: June 25, 2009Inventors: Kenchi ITO, Jun Hayakawa, Katsuya Miura
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Patent number: 7508625Abstract: A magnetic recording device which can write magnetic information with high density. The device uses, for a magnetic recording layer of a magnetic recording medium, a magnetic material whose anisotropy energy varies with an applied electric field. The head has an electrode for applying an electric field to a recording area of the magnetic recording medium. Magnetic recording is performed by applying an AC electric field from the electrode while a DC magnetic field is applied to the recording area of the magnetic recording layer.Type: GrantFiled: January 29, 2007Date of Patent: March 24, 2009Assignee: Hitachi, Ltd.Inventors: Hiromasa Takahashi, Kenchi Ito
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Patent number: 7443718Abstract: A magnetic memory device comprises a magnetic tunnel junction (MTJ) having a ferromagnetic free layer, and exhibits a first, relatively high resistance state, and a second, relatively low resistance state. To write to the magnetic memory device a current IMTJ is driven through the MTJ. For a first duration, the current is equal to a DC threshold current, being the DC current required to switch the multilayer structure between the first state and the second state. This induces a C-like domain structure in the free layer. For a second duration, the current IMTJ is larger than the DC threshold current. This causes the MTJ to switch states. The current requited to cause switching is less than that required using a uniform current pulse.Type: GrantFiled: November 30, 2006Date of Patent: October 28, 2008Assignee: Hitachi, Ltd.Inventors: Kenchi Ito, Hiromasa Takahashi, Takayuki Kawahara, Riichiro Takemura
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Patent number: 7436613Abstract: A magnetic recording device which can write magnetic information with high density. The device uses, for a magnetic recording layer of a magnetic recording medium, a magnetic material whose anisotropy energy varies with an applied electric field. The head has an electrode for applying an electric field to a recording area of the magnetic recording medium. Magnetic recording is performed by applying an AC electric field from the electrode while a DC magnetic field is applied to the recording area of the magnetic recording layer.Type: GrantFiled: March 1, 2007Date of Patent: October 14, 2008Assignee: Hitachi, Ltd.Inventors: Hiromasa Takahashi, Kenchi Ito
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Patent number: 7349186Abstract: A TMR head capable of reconciling high output with high band width is implemented. To that end, two multilayered films each comprised of an insulating layer and a ferromagnetic layer are formed at different locations on an electrode layer, and a current is caused to flow from the ferromagnetic layer of a first multilayered film to the electrode layer while polarized spin is diffused up to a portion of the electrode layer, directly underneath the other multilayered film comprised of the insulating layer and the ferromagnetic layer, thereby detecting a change in resistance, according to a change in the magnetization direction of the ferromagnetic layer of a second multilayered film by use of a circuit extremely large in input impedance, such as a FET.Type: GrantFiled: December 20, 2004Date of Patent: March 25, 2008Assignee: Hitachi, Ltd.Inventor: Kenchi Ito