专利汇可以提供System for adjusting bias of relative magnetizations of ferromagnetic layers in a magnetoresistive sensor专利检索,专利查询,专利分析的服务。并且A magnetoresistive sensing system includes a current-perpendicular-to-the-plane magnetoresistive (CPP-MR) read head and adjustable biasing circuitry connected to the read head for adjusting the relative magnetizations of one or more of the ferromagnetic layers in the read head. The biasing circuitry generates a bias current in the read head that generates a bias-adjusting magnetic field that acts on one or more of the ferromagnetic layers. For a conventional read head, the bias-adjusting field acts orthogonal to the field from the reference layer to change the angle between the magnetization of the free layer and the magnetization of the reference layer. For a scissoring-type read head, the bias-adjusting field acts parallel to the transverse bias field to change the angle between the magnetizations of the two free layers. This results in an improvement in the sensitivity of the read head to bring the soft error rate (SER) below an acceptable level.,下面是System for adjusting bias of relative magnetizations of ferromagnetic layers in a magnetoresistive sensor专利的具体信息内容。
What is claimed:
1. Field of the Invention
The invention relates generally to magnetoresistive (MR) sensors, and more particularly to a system that adjusts the bias of the relative magnetizations (i.e., magnetic moment or magnetization directions or vectors) of the ferromagnetic layers in the sensors.
2. Background of the Invention
One type of conventional MR sensor used as the read head in magnetic recording disk drives is a “spin-valve” sensor based on the giant magnetoresistance (GMR) effect. A GMR spin-valve sensor has a stack of layers that includes two ferromagnetic layers separated by a nonmagnetic electrically conductive spacer layer, which is typically copper (Cu), silver (Ag) or a Cu or Ag alloy. One ferromagnetic layer adjacent the spacer layer has its magnetization direction fixed, such as by being pinned by exchange coupling with an adjacent antiferromagnetic layer, and is referred to as the reference layer. The other ferromagnetic layer adjacent the spacer layer has its magnetization direction free to rotate in the presence of an external magnetic field and is referred to as the free layer. With a sense current applied to the sensor, the rotation of the free-layer magnetization relative to the reference-layer magnetization due to the presence of an external magnetic field is detectable as a change in electrical resistance. If the sense current is directed perpendicularly through the planes of the layers in the sensor stack, the sensor is referred to as a current-perpendicular-to-the-plane (CPP) sensor.
In addition to CPP-GMR read heads, another type of CPP-MR sensor is a magnetic tunnel junction sensor, also called a tunneling MR or TMR sensor, in which the nonmagnetic spacer layer is a very thin nonmagnetic tunnel barrier layer. In a CPP-TMR sensor the current tunneling perpendicularly through the layers depends on the relative orientation of the magnetizations in the two ferromagnetic layers. In a CPP-TMR read head the nonmagnetic spacer layer is formed of an electrically insulating material, such as MgO, TiO2, or Al2O3.
A type of CPP sensor has been proposed that does not have a ferromagnetic reference layer with a fixed or pinned magnetization direction, but instead has dual ferromagnetic sensing or free layers separated by a nonmagnetic spacer layer. In the absence of an applied magnetic field, the magnetizations of the two free layers are oriented generally orthogonal to one another with parallel magnetization components in the sensing direction of the magnetic field to be detected and antiparallel components in the orthogonal direction. With a sense current applied perpendicularly to the layers in the sensor stack and in the presence of an applied magnetic field in the sensing direction, the two magnetizations rotate in opposite directions, changing their angle relative to one another, which is detectable as a change in electrical resistance. Because of this type of behavior of the magnetizations of the two free layers, this type of CPP sensor is often referred to as a “scissoring-type” of CPP sensor. If a CPP-GMR scissoring-type sensor is desired the nonmagnetic spacer layer is an electrically conducting metal or metal alloy. If a CPP-TMR scissoring-type sensor is desired the spacer layer is an electrically insulating material. In a scissoring-type CPP-MR sensor, a “hard-bias” layer of ferromagnetic material located at the back edge of the sensor (opposite the air-bearing surface) applies an approximately fixed, transverse magnetic “bias” field to the sensor. Its purpose is to bias the magnetizations of the two free layers so that they are approximately orthogonal to one another in the quiescent state, i.e., in the absence of an applied magnetic field. Without the hard bias layer, the magnetization directions of the two free layers would tend to be oriented antiparallel to one another. This tendency to be oriented antiparallel results from strong magnetostatic interaction between the two free layers once they have been patterned to sensor dimensions, but may also be the result of exchange coupling between the magnetic layers through the spacer layer. A scissoring-type of CPP-MR sensor is described in U.S. Pat. No. 7,035,062 B2; U.S. Pat. No. 8,670,217 B1 and U.S. Pat. No. 8,015,694 B2.
In both conventional and scissoring-type MR sensors, as the sensor size decreases with the demand for increased data density, the effect of thermomagnetic noise increases, which increases the soft error rate (SER) in the readback data signal. It is thus necessary that the sensors be manufactured with precise dimensions and magnetic properties. However, it is difficult to manufacture large volumes of sensors with identical dimensions and magnetic properties, which means that there may be a wide variation in SER among the sensors.
What is needed is a system that can adjust the bias of the ferromagnetic layers' magnetizations relative to one another after the sensors have been manufactured and installed in the disk drives, so that each sensor will have an acceptable SER.
Embodiments of the invention relate to a magnetoresistive sensing system that includes a current-perpendicular-to-the-plane magnetoresistive (CPP-MR) read head and adjustable biasing circuitry connected to the read head for adjusting the relative magnetizations of one or more of the ferromagnetic layers in the read head. The read head may be a conventional read head with a free and reference ferromagnetic layer or a scissoring-type read head with two free ferromagnetic layers. After the read heads have been manufactured and the sliders that support the read heads installed in the disk drive, certain data tracks are written with a special predetermined pattern and then read back by the read heads. The readback data is detected to measure the soft error rate (SER) for each read head, using well-known techniques. If the measured SER is greater than an acceptable value for a read head, a voltage bias source in the adjustable biasing circuitry is set to a specific value. The biasing circuitry generates a bias current in the read head that generates a bias-adjusting magnetic field that acts on one or more of the ferromagnetic layers to change the relative magnetizations (i.e., magnetic moments or magnetization directions or vectors) of the ferromagnetic layers. This results in an improvement in the sensitivity of the read head to thus bring the SER below an acceptable level. In the case of a conventional read head, the bias-adjusting field acts orthogonal to the field from the reference or pinned ferromagnetic layer to change the angle between the magnetization of the free layer and the magnetization of the reference layer. In the case of a scissoring-type read head, the bias-adjusting field acts parallel to the transverse bias field to increase or decrease the total transverse bias field and thus change the angle between the magnetizations of the two free layers.
For a fuller understanding of the nature and advantages of the present invention, reference should be made to the following detailed description taken together with the accompanying figures.
The disk drive 10 includes a rigid base 12 supporting a spindle 14 that supports a stack of disks, including top disk 16. The spindle 14 is rotated by a spindle motor (not shown) for rotating the disks in the direction shown by curved arrow 17. Disk drive 10 also includes a rotary actuator assembly 40 rotationally mounted to the base 12 at a pivot point 41. The actuator assembly 40 is a voice coil motor (VCM) actuator that includes a magnet assembly 42 fixed to base 12 and a voice coil 43. When energized by control circuitry (not shown) the voice coil 43 moves and thereby rotates E-block 24 with attached arms 22 and load beam assemblies 20 to position the read/write heads 29 to the data tracks on the disks. Each read/write head is located on the trailing surface of an air-bearing slider 31. Each load beam assembly 20 has an integrated lead suspension (ILS) 30 with an array of electrically conductive lines or traces 32 that connect to a read/write head 29 on slider 31. The traces 32 connect at one end to the read/write head 29 and at the other end through a short flex cable to a read amplifier/write driver 50 (preamp), which is typically implemented as an integrated circuit, secured to a side of the E-block 24. Each read/write head 29 includes an inductive write head (not shown) and a magnetoresistive read head (not shown). The preamp 50 receives write data input signals from the disk drive's system-on-a-chip (SOC) (not shown) that is typically located on the backside of base 12. The SOC is connected to preamp 50 by a flex cable 52 and through its electronic packaging, printed circuit board, and flex connector (not shown). While only one disk surface and associated head is depicted in
In embodiments of this invention the MR read head 60 is a current-perpendicular-to-the-plane (CPP) read head that may be a conventional read head with a free and reference ferromagnetic layer or a scissoring-type read head with two free ferromagnetic layers. Embodiments of the invention include adjustable biasing circuitry connected to the read heads. After the read heads have been manufactured and the sliders installed in the disk drive, certain data tracks are written with a special predetermined pattern and then read back by the read heads. The readback data is detected to measure the soft error rate (SER) for each read head, using well-known techniques. If the measured SER is greater than an acceptable value for a read head, a voltage bias source in the adjustable biasing circuitry is set to a specific value. The biasing circuitry generates a bias current in the read head that generates a bias-adjusting magnetic field that acts on one or more of the ferromagnetic layers to change the relative magnetizations (i.e., magnetic moments or magnetization directions or vectors) of the ferromagnetic layers. This results in an improvement in the sensitivity of the read head to thus bring the SER below an acceptable level.
FL1 and FL2 are typically formed of conventional ferromagnetic materials like crystalline CoFe or NiFe alloys, or a multilayer of these materials, such as a CoFe/NiFe bilayer. Instead of these conventional ferromagnetic materials, FL1 and FL2 may be formed of or comprise a ferromagnetic Heusler alloy, some of which are known to exhibit high spin-polarization in their bulk form. Examples of Heusler alloys include but are not limited to the full Heusler alloys Co2MnX (where X is one or more of Al, Sb, Si, Sn, Ga, or Ge). Examples also include but are not limited to the half Heusler alloys NiMnSb, PtMnSb, and Co2FexCr(1-x)Al (where x is between 0 and 1).
FL1 and FL2 comprise self-referenced free layers, and hence no pinned or reference layers with fixed magnetizations are required, unlike in conventional CPP MR sensors. FL1 and FL2 have their magnetizations 151, 171, respectively, oriented in-plane and preferably generally orthogonal to one another in the absence of an applied magnetic field. While the magnetizations 151, 171 in the quiescent state (the absence of an applied magnetic field) are preferably oriented generally orthogonal, i.e., between about 70 and 90 degrees to each other, they may be oriented by less than generally orthogonal, depending on the bias point at which the sensor is operated. FL1 and FL2 are separated by a nonmagnetic spacer layer 160. In other embodiments spacer layer 160 is a nonmagnetic electrically conductive metal or metal alloy, like Cu, Au, Ag, Ru, Rh, Cr and their alloys, if the sensor is a CPP GMR sensor, and a nonmagnetic insulating material, like TiO2, MgO or Al2O3, if the sensor is a CPP TMR sensor.
Located between the lower shield layer S1 and the FL1 is an underlayer or seed layer 140. The seed layer 140 may be a single layer or multiple layers of different materials. Located between FL2 and the upper shield layer S2 is a nonmagnetic electrically conducting capping layer 180. An electrical lead layer S2a is located on capping layer 180 and serves as the electrical lead for the biasing current. Lead layer S2a may be formed of a soft magnetic material like that used for shields S1 and S2. The bottom shield S1 and S2a are used as leads, with S1 serving as the substrate for the deposition of the sensor stack. The underlayer or seed layer 140 is typically one or more layers of NiFeCr, NiFe, Ta, Cu or Ru. The capping layer 180 provides corrosion protection and is typically formed of single layers, like Ru or Ta, or multiple layers of different materials, such as a Cu/Ru/Ta trilayer.
In the exchange-coupled side shield 200, which is identical to side shield 250, soft magnetic layers 210, 220 are separated by a nonmagnetic antiparallel-coupling (APC) layer 215, typically a 0.5-1 nm thick layer of Ru or Cr. The thickness of the APC layer 215 is chosen to provide adequate antiferromagnetic exchange coupling, resulting in the magnetizations 211, 221 of soft magnetic layers 210, 220 being oriented substantially antiparallel.
Thus layers 210, 220 (and also layers 260, 270 in exchange-coupled soft side shield 250) are preferably an alloy comprising Ni and Fe with permeability (μ) preferably greater than 10. Any of the known materials suitable for use in the along-the-track shields S1 and S2 may be used for layers 210, 220. Specific compositions include NiFex, where x is between 1 and 25, and (NiFex)Moy or (NiFex)Cry, where y is between 1 and 8, where the subscripts are in atomic percent.
As shown in
The example illustrated in
While the magnetic moments 351, 371 in the quiescent state are preferably oriented generally orthogonal, i.e., between about 70 and 90 degrees to each other, they may be oriented by less than generally orthogonal, depending on the bias point at which the sensor is operated. Free layer 350 and reference layer 370 are separated by a nonmagnetic spacer layer 360. Spacer layer 360 is a nonmagnetic electrically conductive metal or metal alloy, like Cu, Au, Ag, Ru, Rh, Cr and their alloys, if the sensor is a CPP GMR sensor, and a nonmagnetic insulating material, like TiO2, MgO or Al2O3, if the sensor is a CPP TMR sensor.
The example illustrated in
While the present invention has been particularly shown and described with reference to the preferred embodiments, it will be understood by those skilled in the art that various changes in form and detail may be made without departing from the spirit and scope of the invention. Accordingly, the disclosed invention is to be considered merely as illustrative and limited in scope only as specified in the appended claims.
标题 | 发布/更新时间 | 阅读量 |
---|---|---|
正畸器具 | 2020-05-08 | 732 |
连接结构及具有其的装置 | 2020-05-08 | 733 |
一种耐腐蚀高熵合金氮化物涂层、其制备方法及应用 | 2020-05-08 | 114 |
一种基于PVD沉积方法的氮化铝陶瓷板和金属的连接方法 | 2020-05-08 | 244 |
液压工具 | 2020-05-11 | 935 |
连接结构及具有其的装置 | 2020-05-08 | 574 |
一种应用于PVD镀膜的弧光电子源增强辉光放电加热工艺 | 2020-05-08 | 213 |
一种提升碳纳米管阵列-碳纳米管膜柔性复合材料场发射性能的方法 | 2020-05-08 | 896 |
一种机械密封结构及泵装置 | 2020-05-08 | 353 |
采用带隙参考机制和相关驱动方法实现的模拟区块 | 2020-05-08 | 557 |
高效检索全球专利专利汇是专利免费检索,专利查询,专利分析-国家发明专利查询检索分析平台,是提供专利分析,专利查询,专利检索等数据服务功能的知识产权数据服务商。
我们的产品包含105个国家的1.26亿组数据,免费查、免费专利分析。
专利汇分析报告产品可以对行业情报数据进行梳理分析,涉及维度包括行业专利基本状况分析、地域分析、技术分析、发明人分析、申请人分析、专利权人分析、失效分析、核心专利分析、法律分析、研发重点分析、企业专利处境分析、技术处境分析、专利寿命分析、企业定位分析、引证分析等超过60个分析角度,系统通过AI智能系统对图表进行解读,只需1分钟,一键生成行业专利分析报告。