scispace - formally typeset
Search or ask a question
Patent•

Shielded magnetic tunnel junction magnetoresistive read head

TL;DR: In this article, the thickness of the spacer layers is selected to optimize the spacing between the shields, which is a parameter that controls the linear resolution of the data that can be read from the magnetic recording medium.
Abstract: A magnetic tunnel junction (MTJ) magnetoresistive read head for a magnetic recording system has the MTJ device located between two spaced-apart magnetic shields. The magnetic shields, which allow the head to detect individual magnetic transitions from the magnetic recording medium without interference from neighboring transitions, also function as electrical leads for connection of the head to sense circuitry. Electrically conductive spacer layers are located at the top and bottom of the MTJ device and connect the MTJ device to the shields. The thickness of the spacer layers is selected to optimize the spacing between the shields, which is a parameter that controls the linear resolution of the data that can be read from the magnetic recording medium. To reduce the likelihood of electrical shorting between the shields if the shield-to-shield spacing is too small, each of the shields can have a pedestal region with the MTJ device located between the two pedestals, so that the shield-to-shield spacing outside the pedestal regions is greater than in the pedestal regions.
Citations
More filters
Journal Article•DOI•
Stuart S. P. Parkin1, Xin Jiang1, Christian Kaiser1, Alex Panchula1, Kevin P. Roche1, Mahesh G. Samant1 •
21 May 2003
TL;DR: The magnetic tunnel junction (MTJ) as discussed by the authors is an example of spintronic materials in which the flow of spin-polarized electrons is manipulated by controlling, via magnetic fields, the orientation of magnetic moments in inhomogeneous magnetic thin film systems.
Abstract: The discovery of enhanced magnetoresistance and oscillatory interlayer exchange coupling in transition metal multilayers just over a decade ago has enabled the development of new classes of magnetically engineered magnetic thin-film materials suitable for advanced magnetic sensors and magnetic random access memories. Magnetic sensors based on spin-valve giant magnetoresistive (GMR) sandwiches with artificial antiferromagnetic reference layers have resulted in enormous increases in the storage capacity of magnetic hard disk drives. The unique properties of magnetic tunnel junction (MTJ) devices has led to the development of an advanced high performance nonvolatile magnet random access memory with density approaching that of dynamic random-access memory (RAM) and read-write speeds comparable to static RAM. Both GMR and MTJ devices are examples of spintronic materials in which the flow of spin-polarized electrons is manipulated by controlling, via magnetic fields, the orientation of magnetic moments in inhomogeneous magnetic thin film systems. More complex devices, including three-terminal hot electron magnetic tunnel transistors, suggest that there are many other applications of spintronic materials.

591 citations

Patent•
15 Nov 2007
TL;DR: In this article, a storage element including a storage layer configured to hold information by use of a magnetization state of a magnetic material, with a pinned magnetization layer being provided on one side of the storage layer, with tunnel insulation layer, and with the direction of magnetization of storage layer being changed through injection of spin polarized electrons by passing a current in the lamination direction.
Abstract: A storage element including a storage layer configured to hold information by use of a magnetization state of a magnetic material, with a pinned magnetization layer being provided on one side of the storage layer, with a tunnel insulation layer, and with the direction of magnetization of the storage layer being changed through injection of spin polarized electrons by passing a current in the lamination direction, so as to record information in the storage layer, wherein a spin barrier layer configured to restrain diffusion of the spin polarized electrons is provided on the side, opposite to the pinned magnetization layer, of the storage layer; and the spin barrier layer includes at least one material selected from the group composing of oxides, nitrides, and fluorides.

357 citations

Patent•
10 Mar 2000
TL;DR: In this paper, the authors present an apparatus for fabricating a magnetic field sensor having a magnetoresistive element, a magnetic bias layer for bias bias, and an electrical insulator positioned between the bias layer and the magnetoregressive element.
Abstract: The apparatus of the present invention is embodied in a magnetic field sensor having a magnetoresistive element, a magnetic bias layer for biasing the magnetoresistive element with a magnetic field, and an electrical insulator positioned between the magnetic bias layer and the magnetoresistive element. The insulator prevents the flow of electrical current between the magnetoresistive element and the magnetic bias layer and at least a portion of the insulator allows passage of the magnetic field from the magnetic bias layer to the magnetoresistive element such that the magnetoresistive element is biased. The method of the present invention is embodied in a method for fabricating a magnetic field sensor having the steps of forming a magnetoresistive element, forming a lower insulator with a main section and an end section over at least a portion of the magnetoresistive element, forming a magnetic bias layer over the main section of the lower insulator, and forming an upper insulator over the magnetic bias layer and over the end section of the lower insulator, such that the magnetic bias layer is electrically insulated from the magnetoresistive element.

199 citations

Patent•
20 May 2002
TL;DR: In this paper, an improved bias magnet-to-magnetoresistive element interface and method of fabrication is presented, where the wall/walls of an MR element opposing a bias layer are formed by over etching to provide vertical side walls without taper.
Abstract: The present invention provides an improved bias magnet-to-magnetoresistive element interface and method of fabrication. In a preferred embodiment, the wall/walls of an MR element opposing a bias layer are formed by over etching to provide vertical side walls without taper. In the preferred embodiment, a protective element is formed over the MR element to protect it during etch processes. In some embodiments, a filler layer is deposited prior to bias layer formation. In CIP embodiments, any portion of the filler layer forming on vertical side walls of the MR element is etched to provide an exposed side wall surface for contiguous bias layer formation. In CPP embodiments, the filler layer forms on a vertical back wall and electrically insulates the MR element from the bias layer. In CIP and CPP embodiments, tapered portions of the bias material, which form overhanging the MR element, are removed by directional etching to improve the direction and stability of the induced longitudinal field within the MR element. In some CIP embodiments, tapered overhang removal allows for formation of improved lead structures, which may be deposited on the MR element closer to the side walls, and which are not pinched off by the overhang of an underlying bias layer, thus improving current density profile and definition of the actual effective track width of the device.

183 citations

Patent•
Song Pang, Lijun Tong1, Zi-Wen Dong1, Kevin K. Lin1, Joyce Hsiang •
26 May 2000
TL;DR: In this article, the authors proposed a read sensor consisting of a shield, a sensor element, an extra gap between the shield and the sensor, and a gap layer between the sensor element and the extra shield.
Abstract: In at least one embodiment, the apparatus of the invention is a read sensor comprising a shield, a sensor element, an extra shield between the shield and the sensor element, an extra gap between the shield and the sensor and adjacent the extra shield, and a gap layer between the sensor element and the extra shield. The sensor element is positioned in a sensor layer. With the extra shield adjacent to the sensor element and separated by only the relatively thin gap layer, high areal recording density and excellent instability of the sensor element is obtained. At the same time, by fabricating the extra shield to be not significantly wider than the sensor element, the potential for shorting is minimized by placing both the gap and the thicker extra gap between the sensor lead elements and the shield. In at least one embodiment, the method of the invention is for fabricating a read sensor and comprises depositing an extra gap layer onto a shield, removing a portion of the extra gap layer to form a cavity, depositing an extra shield into the cavity, planarizing the extra gap and the extra shield, depositing a gap layer onto the extra gap and the extra shield, and depositing a sensor element onto the gap layer and adjacent to the extra shield.

152 citations

References
More filters
Patent•
18 Mar 1996
TL;DR: In this paper, a magnetic tunnel junction (MTJ) device is used as a magnetic field sensor or as a memory cell in a magnetic random access (MRAM) array.
Abstract: A magnetic tunnel junction (MTJ) device is usable as a magnetic field sensor or as a memory cell in a magnetic random access (MRAM) array. The MTJ device has a "pinned" ferromagnetic layer whose magnetization is oriented in the plane of the layer but is fixed so as to not be able to rotate in the presence of an applied magnetic field in the range of interest, a "free" ferromagnetic layer whose magnetization is able to be rotated in the plane of the layer relative to the fixed magnetization of the pinned ferromagnetic layer, and an insulating tunnel barrier layer located between and in contact with both ferromagnetic layers. The pinned ferromagnetic layer is pinned by interfacial exchange coupling with an adjacent antiferromagnetic layer. The amount of tunneling current that flows perpendicularly through the two ferromagnetic layers and the intermediate tunnel barrier layer depends on the relative magnetization directions of the two ferromagnetic layers. The ferromagnetic layers are formed in two separate spaced-apart planes that do not overlap in the region of the tunnel barrier layer, thereby eliminating any extraneous magnetic poles.

208 citations

Patent•
Robert E. Fontana1, Stuart S. P. Parkin1•
27 Nov 1996
TL;DR: A magnetic tunnel junction device for use as a magnetic memory cell or a magnetic field sensor has one fixed ferromagnetic layer and one sensing magnetometer on opposite sides of the insulating tunnel barrier layer.
Abstract: A magnetic tunnel junction device for use as a magnetic memory cell or a magnetic field sensor has one fixed ferromagnetic layer and one sensing ferromagnetic layer formed on opposite sides of the insulating tunnel barrier layer, and a hard biasing ferromagnetic layer that is electrically insulated from but yet magnetostatically coupled with the sensing ferromagnetic layer. The magnetic tunnel junction in the device is formed on an electrical lead on a substrate and is made up of a stack of layers. The layers in the stack are an antiferromagnetic layer, a fixed ferromagnetic layer exchange biased with the antfferromagnetic layer so that its magnetic moment cannot rotate in the presence of an applied magnetic field, an insulating tunnel barrier layer in contact with the fixed ferromagnetic layer, and a sensing ferromagnetic layer in contact with the tunnel barrier layer and whose magnetic moment is free to rotate in the presence of an applied magnetic field. The stack is generally rectangularly shaped with parallel side edges. A layer of hard biasing ferromagnetic material is located near to but spaced from the side edges of the sensing ferromagnetic layer to longitudinally bias the magnetic moment of the sensing ferromagnetic layer in a preferred direction. A layer of electrically insulating material isolates the hard biasing material from the electrical lead and the sensing ferromagnetic layer so that sense current is not shunted to the hard biasing material but is allowed to flow perpendicularly through the layers in the stack.

180 citations

Patent•
24 Oct 1994
TL;DR: The magnetoresistance effect element is of a multilayered structure having at least magnetic layers and an intermediate layer of an insulating material, a semiconductor or an antiferromagnetic material against the magnetic layers, so that a current flows in the intermediate layer as discussed by the authors.
Abstract: The magnetoresistance effect element is of a multilayered structure having at least magnetic layers and an intermediate layer of an insulating material, a semiconductor or an antiferromagnetic material against the magnetic layers, and the magnetoresistance effect element has terminals formed at least on the opposite magnetic layers, respectively, so that a current flows in the intermediate layer. The film surfaces of all the magnetic layers constituting the magnetoresistance effect element are opposed substantially at right angles to the recording surface of a magnetic recording medium. Therefore, the area of the magnetic layers facing the recording surface of the magnetic recording medium can be extremely reduced, and thus the magnetic field from a very narrow region of the high-density recorded magnetic recording medium can be detected by the current which has a tunneling characteristic and passes through the intermediate layer.

114 citations

Patent•
21 Dec 1993
TL;DR: In this article, the MR element of such arrangement offers a surprisingly large MR ratio under application of a sufficiently low magnetic field despite such a simple arrangement thereof, despite the fact that a simple three-layer structure has a relatively small MR ratio.
Abstract: A MR element which has a basically three-layered structure wherein the first and the second magnetic layer sandwich the nonmagnetic layer or of a basically five-layered structure wherein nonmagnetic layers are sandwiched between the first and second magnetic layers and between the second and third magnetic layers, respectively. The MR element of such arrangement offers a surprisingly large MR ratio under application of a sufficiently low magnetic field despite such a simple arrangement thereof.

100 citations

Patent•
21 Mar 1995
TL;DR: Ferromagnetic/insulator/ferromagnetic tunneling has been shown to give over 10% change in the junction resistance with H less than 100 Oe, at room temperature but decreases at high dc-bias across the junction.
Abstract: Ferromagnetic/insulator/ferromagnetic tunneling has been shown to give over 10% change in the junction resistance with H less than 100 Oe, at room temperature but decreases at high dc-bias across the junction. Using such junctions as magnetic sensors or memory elements would have several advantages; it is a trilayer device and does not strongly depend on the thickness of FM electrodes or the tunnel barrier; submicron size is possible with high junction resistance and low power dissipation. The magnitude of the effect is consistent with the simple model of spin-polarized tunneling between ferromagnets.

68 citations