The Experts below are selected from a list of 177 Experts worldwide ranked by ideXlab platform
A K Petfordlong - One of the best experts on this subject based on the ideXlab platform.
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magnetic viscosity effects on the pinned layer loop of spin Valve Materials
Journal of Applied Physics, 2000Co-Authors: A M Goodman, H Laidler, K Ogrady, N W Owen, A K PetfordlongAbstract:In this work, we report on measurements of magnetization with time [M(t)] around the pinned layer loop in spin-Valve Materials. These time-dependent effects are manifest via changes in M(t) in constant field (H) and via variations in the apparent coercivity with the sweep-rate of the applied field. The changes in the apparent coercivity on the pinned layer loop differ for the magnetizing and demagnetizing branches as does the form of M(t) data.
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electron microscopy studies of spin Valve Materials
Journal of Physics D, 1999Co-Authors: X Portier, A K PetfordlongAbstract:Since the discovery of the giant magnetoresistance effect and more recently its application in magnetic recording technology, the interest in spin-Valve (SV) structures used in devices such as magnetoresistive sensors and random access memories, has increased greatly. As the size of these devices becomes smaller and smaller, the need to investigate the local microstructure and the micromagnetic behaviour of SV Materials becomes obvious. High-resolution electron microscopy (HREM) analyses have been carried out to investigate the microstructure of these metallic layered films. The choice of the Materials used is crucial for the resulting magnetic properties. After a summary of the most common configurations found in the literature and some comments on their advantages and disadvantages, we will present some HREM studies which have clarified the differences in magnetic properties between top and bottom SVs. The growth conditions, the use of a seed layer and the thermal behaviour of SVs annealed at different temperatures will be discussed. In addition, some magnetostatic effects have been explained by microstructural considerations. In addition to the HREM experiments, one of the techniques enabling micromagnetic studies at the micron scale to be carried out is Lorentz transmission electron microscopy (LTEM). This technique, which allows the magnetic domain structure of a magnetic material to be observed in situ, has been improved over the past few years. Very recently, the development of in situ magnetizing experiments in LTEM has enabled us to apply simultaneously an external field as well as a current through an SV element during the observation of the magnetization reversal. As a result, both electronic properties, via the giant magnetoresistance (GMR) curve, and local magnetic properties, via observation of the domain structure, can be analysed and correlated. Furthermore, the use of a mapping technique which allows quantitative analysis of the in-plane magnetization of the SV element, based on the analysis of Foucault images, has shown a clear correlation between the resistance values and the domain structure of the element. Such facilities have also resulted in a better understanding of the behaviour of various SV elements under real operating conditions. In particular, the effect on the reversal mechanism of the current density, the stray-field coupling at the edges of the element for different shapes of elements and the current direction through the element have been carefully studied.
Jim Daughton - One of the best experts on this subject based on the ideXlab platform.
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360 spl deg angle sensor using spin Valve Materials with saf structure
IEEE Transactions on Magnetics, 2005Co-Authors: Dexin Wang, Jay Brown, Tim Hazelton, Jim DaughtonAbstract:Microchips of 360/spl deg/ angle sensors using spin Valve Materials were designed, fabricated, and tested with excellent performance. The spin Valve material used for the angle sensor has a structure of Ta-NiFeCo-CoFe-Cu-CoFe-Ru-CoFe-CrMnPt. External magnetic fields have little torque on the CoFe-Ru-CoFe structure up to at least 500Oe, which is the highest value available during the test. This is due to the strong antiparallel exchange coupling between the two CoFe sublayers of the same thickness via a thin layer of Ru and the resulting zero net magnetic moment. There is a sharp switching of the free layer with a low coercivity of 4 Oe along the easy axis. Both the high standoff field and small coercivity ensure that the sensor operates properly with large tolerance in mechanical assembly. The angle sensor is used stationary in combination with a disc-shaped permanent magnet attached to a rotating shaft near the sensor. The permanent magnet is magnetized in-plane, thus creating a field that is rotating with the shaft. The magnetic field from the permanent magnet forces the free layer magnetization to follow the field and rotate with it. With a fixed reference layer magnetization and an in-phase following of the free layer magnetization, the magnetoresistance is a simple cosine function of the angle between the rotating permanent magnet and the stationary sensor. A special Wheatstone-bridge with four spin Valve resistors is used to compensate the thermal drift expected in application environments. One half bridge has a 90/spl deg/ phase delay from the other, resulting in a cosine and a sine function, in combination to uniquely determine any angular relationship between the permanent magnet and the sensor between 0 to 360/spl deg/.
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Angle sensor using spin Valve with SAF structure
2005 IEEE International Magnetics Conference (INTERMAG), 2005Co-Authors: Dexin Wang, Jay Brown, Tim Hazelton, Jim DaughtonAbstract:An angle sensor using spin Valve Materials was designed, fabricated and tested. The spin Valve material, composed of a top-pinned synthetic antiferromagnet layer for better standoff fields and a composite free layer for low coercivity and high magnetoresistance, has a structure of Ta-NiFeCo-CoFe-Cu-CoFe-Ru-CoFe-CrMnPt. The spin Valve film showed switching of the free layer with low coercivity (5 Oe) and a plateau of the high field region (up to 500 Oe) after annealing at 250/spl deg/C for 1 hour. Two half-Wheatstone-bridges provide cosine and sine functions to uniquely determine angular positions between the angle sensor and a disc-shaped permanent magnet from 0 to 360 degrees at 2-6 mm airgap values.
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360° angle sensor using spin Valve Materials with SAF structure
IEEE Transactions on Magnetics, 2005Co-Authors: Dexin Wang, Jay Brown, Tim Hazelton, Jim DaughtonAbstract:Microchips of 360 degrees angle sensors using spin Valve Materials were\ndesigned, fabricated, and tested with excellent performance. The spin\nValve material used for the angle sensor has a structure of\nTa-NiFeCo-CoFe-Cu-CoFe-Ru-CoFe-CrMnPt. External magnetic fields have\nlittle torque on the CoFe-Ru-CoFe structure upto at least 500Oe, which\nis the highest value available during the test. This is due to the\nstrong antiparallel exchange coupling between the two CoFe sublayers of\nthe same thickness via a thin layer of Ru and the resulting zero net\nmagnetic moment. There is a sharp switching of the free layer with a\nlow coercivity of 4 Oe along the easy axis. Both the high standoff\nfield and small coercivity ensure that the sensor operates properly\nwith large tolerance in mechanical assembly. The angle sensor is used\nstationary in combination with a disc-shaped permanent magnet attached\nto a rotating shaft near the sensor. The permanent magnet is magnetized\nin-plane, thus creating a field that is rotating with the shaft. The\nmagnetic field from the permanent magnet forces the free layer\nmagnetization to follow the field and rotate with it. With a fixed\nreference layer magnetization and an in-phase following of the free\nlayer magnetization, the magnetoresistance is a simple cosine function\nof the angle between the rotating permanent magnet and the stationary\nsensor. A special Wheatstone-bridge with four spin Valve resistors is\nused to compensate the thermal drift expected in application\nenvironments. One half bridge has a 90 degrees phase delay from the\nother, resulting in a cosine and a sine function, in combination to\nuniquely determine any angular relationship between the permanent\nmagnet and the sensor between 0 to 360 degrees.
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360/spl deg/ angle sensor using spin Valve Materials with SAF structure
IEEE Transactions on Magnetics, 2005Co-Authors: Dexin Wang, Jay Brown, Tim Hazelton, Jim DaughtonAbstract:Microchips of 360/spl deg/ angle sensors using spin Valve Materials were designed, fabricated, and tested with excellent performance. The spin Valve material used for the angle sensor has a structure of Ta-NiFeCo-CoFe-Cu-CoFe-Ru-CoFe-CrMnPt. External magnetic fields have little torque on the CoFe-Ru-CoFe structure up to at least 500Oe, which is the highest value available during the test. This is due to the strong antiparallel exchange coupling between the two CoFe sublayers of the same thickness via a thin layer of Ru and the resulting zero net magnetic moment. There is a sharp switching of the free layer with a low coercivity of 4 Oe along the easy axis. Both the high standoff field and small coercivity ensure that the sensor operates properly with large tolerance in mechanical assembly. The angle sensor is used stationary in combination with a disc-shaped permanent magnet attached to a rotating shaft near the sensor. The permanent magnet is magnetized in-plane, thus creating a field that is rotating with the shaft. The magnetic field from the permanent magnet forces the free layer magnetization to follow the field and rotate with it. With a fixed reference layer magnetization and an in-phase following of the free layer magnetization, the magnetoresistance is a simple cosine function of the angle between the rotating permanent magnet and the stationary sensor. A special Wheatstone-bridge with four spin Valve resistors is used to compensate the thermal drift expected in application environments. One half bridge has a 90/spl deg/ phase delay from the other, resulting in a cosine and a sine function, in combination to uniquely determine any angular relationship between the permanent magnet and the sensor between 0 to 360/spl deg/.
Dexin Wang - One of the best experts on this subject based on the ideXlab platform.
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360 spl deg angle sensor using spin Valve Materials with saf structure
IEEE Transactions on Magnetics, 2005Co-Authors: Dexin Wang, Jay Brown, Tim Hazelton, Jim DaughtonAbstract:Microchips of 360/spl deg/ angle sensors using spin Valve Materials were designed, fabricated, and tested with excellent performance. The spin Valve material used for the angle sensor has a structure of Ta-NiFeCo-CoFe-Cu-CoFe-Ru-CoFe-CrMnPt. External magnetic fields have little torque on the CoFe-Ru-CoFe structure up to at least 500Oe, which is the highest value available during the test. This is due to the strong antiparallel exchange coupling between the two CoFe sublayers of the same thickness via a thin layer of Ru and the resulting zero net magnetic moment. There is a sharp switching of the free layer with a low coercivity of 4 Oe along the easy axis. Both the high standoff field and small coercivity ensure that the sensor operates properly with large tolerance in mechanical assembly. The angle sensor is used stationary in combination with a disc-shaped permanent magnet attached to a rotating shaft near the sensor. The permanent magnet is magnetized in-plane, thus creating a field that is rotating with the shaft. The magnetic field from the permanent magnet forces the free layer magnetization to follow the field and rotate with it. With a fixed reference layer magnetization and an in-phase following of the free layer magnetization, the magnetoresistance is a simple cosine function of the angle between the rotating permanent magnet and the stationary sensor. A special Wheatstone-bridge with four spin Valve resistors is used to compensate the thermal drift expected in application environments. One half bridge has a 90/spl deg/ phase delay from the other, resulting in a cosine and a sine function, in combination to uniquely determine any angular relationship between the permanent magnet and the sensor between 0 to 360/spl deg/.
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Angle sensor using spin Valve with SAF structure
2005 IEEE International Magnetics Conference (INTERMAG), 2005Co-Authors: Dexin Wang, Jay Brown, Tim Hazelton, Jim DaughtonAbstract:An angle sensor using spin Valve Materials was designed, fabricated and tested. The spin Valve material, composed of a top-pinned synthetic antiferromagnet layer for better standoff fields and a composite free layer for low coercivity and high magnetoresistance, has a structure of Ta-NiFeCo-CoFe-Cu-CoFe-Ru-CoFe-CrMnPt. The spin Valve film showed switching of the free layer with low coercivity (5 Oe) and a plateau of the high field region (up to 500 Oe) after annealing at 250/spl deg/C for 1 hour. Two half-Wheatstone-bridges provide cosine and sine functions to uniquely determine angular positions between the angle sensor and a disc-shaped permanent magnet from 0 to 360 degrees at 2-6 mm airgap values.
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360° angle sensor using spin Valve Materials with SAF structure
IEEE Transactions on Magnetics, 2005Co-Authors: Dexin Wang, Jay Brown, Tim Hazelton, Jim DaughtonAbstract:Microchips of 360 degrees angle sensors using spin Valve Materials were\ndesigned, fabricated, and tested with excellent performance. The spin\nValve material used for the angle sensor has a structure of\nTa-NiFeCo-CoFe-Cu-CoFe-Ru-CoFe-CrMnPt. External magnetic fields have\nlittle torque on the CoFe-Ru-CoFe structure upto at least 500Oe, which\nis the highest value available during the test. This is due to the\nstrong antiparallel exchange coupling between the two CoFe sublayers of\nthe same thickness via a thin layer of Ru and the resulting zero net\nmagnetic moment. There is a sharp switching of the free layer with a\nlow coercivity of 4 Oe along the easy axis. Both the high standoff\nfield and small coercivity ensure that the sensor operates properly\nwith large tolerance in mechanical assembly. The angle sensor is used\nstationary in combination with a disc-shaped permanent magnet attached\nto a rotating shaft near the sensor. The permanent magnet is magnetized\nin-plane, thus creating a field that is rotating with the shaft. The\nmagnetic field from the permanent magnet forces the free layer\nmagnetization to follow the field and rotate with it. With a fixed\nreference layer magnetization and an in-phase following of the free\nlayer magnetization, the magnetoresistance is a simple cosine function\nof the angle between the rotating permanent magnet and the stationary\nsensor. A special Wheatstone-bridge with four spin Valve resistors is\nused to compensate the thermal drift expected in application\nenvironments. One half bridge has a 90 degrees phase delay from the\nother, resulting in a cosine and a sine function, in combination to\nuniquely determine any angular relationship between the permanent\nmagnet and the sensor between 0 to 360 degrees.
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360/spl deg/ angle sensor using spin Valve Materials with SAF structure
IEEE Transactions on Magnetics, 2005Co-Authors: Dexin Wang, Jay Brown, Tim Hazelton, Jim DaughtonAbstract:Microchips of 360/spl deg/ angle sensors using spin Valve Materials were designed, fabricated, and tested with excellent performance. The spin Valve material used for the angle sensor has a structure of Ta-NiFeCo-CoFe-Cu-CoFe-Ru-CoFe-CrMnPt. External magnetic fields have little torque on the CoFe-Ru-CoFe structure up to at least 500Oe, which is the highest value available during the test. This is due to the strong antiparallel exchange coupling between the two CoFe sublayers of the same thickness via a thin layer of Ru and the resulting zero net magnetic moment. There is a sharp switching of the free layer with a low coercivity of 4 Oe along the easy axis. Both the high standoff field and small coercivity ensure that the sensor operates properly with large tolerance in mechanical assembly. The angle sensor is used stationary in combination with a disc-shaped permanent magnet attached to a rotating shaft near the sensor. The permanent magnet is magnetized in-plane, thus creating a field that is rotating with the shaft. The magnetic field from the permanent magnet forces the free layer magnetization to follow the field and rotate with it. With a fixed reference layer magnetization and an in-phase following of the free layer magnetization, the magnetoresistance is a simple cosine function of the angle between the rotating permanent magnet and the stationary sensor. A special Wheatstone-bridge with four spin Valve resistors is used to compensate the thermal drift expected in application environments. One half bridge has a 90/spl deg/ phase delay from the other, resulting in a cosine and a sine function, in combination to uniquely determine any angular relationship between the permanent magnet and the sensor between 0 to 360/spl deg/.
Jay Brown - One of the best experts on this subject based on the ideXlab platform.
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360 spl deg angle sensor using spin Valve Materials with saf structure
IEEE Transactions on Magnetics, 2005Co-Authors: Dexin Wang, Jay Brown, Tim Hazelton, Jim DaughtonAbstract:Microchips of 360/spl deg/ angle sensors using spin Valve Materials were designed, fabricated, and tested with excellent performance. The spin Valve material used for the angle sensor has a structure of Ta-NiFeCo-CoFe-Cu-CoFe-Ru-CoFe-CrMnPt. External magnetic fields have little torque on the CoFe-Ru-CoFe structure up to at least 500Oe, which is the highest value available during the test. This is due to the strong antiparallel exchange coupling between the two CoFe sublayers of the same thickness via a thin layer of Ru and the resulting zero net magnetic moment. There is a sharp switching of the free layer with a low coercivity of 4 Oe along the easy axis. Both the high standoff field and small coercivity ensure that the sensor operates properly with large tolerance in mechanical assembly. The angle sensor is used stationary in combination with a disc-shaped permanent magnet attached to a rotating shaft near the sensor. The permanent magnet is magnetized in-plane, thus creating a field that is rotating with the shaft. The magnetic field from the permanent magnet forces the free layer magnetization to follow the field and rotate with it. With a fixed reference layer magnetization and an in-phase following of the free layer magnetization, the magnetoresistance is a simple cosine function of the angle between the rotating permanent magnet and the stationary sensor. A special Wheatstone-bridge with four spin Valve resistors is used to compensate the thermal drift expected in application environments. One half bridge has a 90/spl deg/ phase delay from the other, resulting in a cosine and a sine function, in combination to uniquely determine any angular relationship between the permanent magnet and the sensor between 0 to 360/spl deg/.
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Angle sensor using spin Valve with SAF structure
2005 IEEE International Magnetics Conference (INTERMAG), 2005Co-Authors: Dexin Wang, Jay Brown, Tim Hazelton, Jim DaughtonAbstract:An angle sensor using spin Valve Materials was designed, fabricated and tested. The spin Valve material, composed of a top-pinned synthetic antiferromagnet layer for better standoff fields and a composite free layer for low coercivity and high magnetoresistance, has a structure of Ta-NiFeCo-CoFe-Cu-CoFe-Ru-CoFe-CrMnPt. The spin Valve film showed switching of the free layer with low coercivity (5 Oe) and a plateau of the high field region (up to 500 Oe) after annealing at 250/spl deg/C for 1 hour. Two half-Wheatstone-bridges provide cosine and sine functions to uniquely determine angular positions between the angle sensor and a disc-shaped permanent magnet from 0 to 360 degrees at 2-6 mm airgap values.
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360° angle sensor using spin Valve Materials with SAF structure
IEEE Transactions on Magnetics, 2005Co-Authors: Dexin Wang, Jay Brown, Tim Hazelton, Jim DaughtonAbstract:Microchips of 360 degrees angle sensors using spin Valve Materials were\ndesigned, fabricated, and tested with excellent performance. The spin\nValve material used for the angle sensor has a structure of\nTa-NiFeCo-CoFe-Cu-CoFe-Ru-CoFe-CrMnPt. External magnetic fields have\nlittle torque on the CoFe-Ru-CoFe structure upto at least 500Oe, which\nis the highest value available during the test. This is due to the\nstrong antiparallel exchange coupling between the two CoFe sublayers of\nthe same thickness via a thin layer of Ru and the resulting zero net\nmagnetic moment. There is a sharp switching of the free layer with a\nlow coercivity of 4 Oe along the easy axis. Both the high standoff\nfield and small coercivity ensure that the sensor operates properly\nwith large tolerance in mechanical assembly. The angle sensor is used\nstationary in combination with a disc-shaped permanent magnet attached\nto a rotating shaft near the sensor. The permanent magnet is magnetized\nin-plane, thus creating a field that is rotating with the shaft. The\nmagnetic field from the permanent magnet forces the free layer\nmagnetization to follow the field and rotate with it. With a fixed\nreference layer magnetization and an in-phase following of the free\nlayer magnetization, the magnetoresistance is a simple cosine function\nof the angle between the rotating permanent magnet and the stationary\nsensor. A special Wheatstone-bridge with four spin Valve resistors is\nused to compensate the thermal drift expected in application\nenvironments. One half bridge has a 90 degrees phase delay from the\nother, resulting in a cosine and a sine function, in combination to\nuniquely determine any angular relationship between the permanent\nmagnet and the sensor between 0 to 360 degrees.
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360/spl deg/ angle sensor using spin Valve Materials with SAF structure
IEEE Transactions on Magnetics, 2005Co-Authors: Dexin Wang, Jay Brown, Tim Hazelton, Jim DaughtonAbstract:Microchips of 360/spl deg/ angle sensors using spin Valve Materials were designed, fabricated, and tested with excellent performance. The spin Valve material used for the angle sensor has a structure of Ta-NiFeCo-CoFe-Cu-CoFe-Ru-CoFe-CrMnPt. External magnetic fields have little torque on the CoFe-Ru-CoFe structure up to at least 500Oe, which is the highest value available during the test. This is due to the strong antiparallel exchange coupling between the two CoFe sublayers of the same thickness via a thin layer of Ru and the resulting zero net magnetic moment. There is a sharp switching of the free layer with a low coercivity of 4 Oe along the easy axis. Both the high standoff field and small coercivity ensure that the sensor operates properly with large tolerance in mechanical assembly. The angle sensor is used stationary in combination with a disc-shaped permanent magnet attached to a rotating shaft near the sensor. The permanent magnet is magnetized in-plane, thus creating a field that is rotating with the shaft. The magnetic field from the permanent magnet forces the free layer magnetization to follow the field and rotate with it. With a fixed reference layer magnetization and an in-phase following of the free layer magnetization, the magnetoresistance is a simple cosine function of the angle between the rotating permanent magnet and the stationary sensor. A special Wheatstone-bridge with four spin Valve resistors is used to compensate the thermal drift expected in application environments. One half bridge has a 90/spl deg/ phase delay from the other, resulting in a cosine and a sine function, in combination to uniquely determine any angular relationship between the permanent magnet and the sensor between 0 to 360/spl deg/.
Tim Hazelton - One of the best experts on this subject based on the ideXlab platform.
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360 spl deg angle sensor using spin Valve Materials with saf structure
IEEE Transactions on Magnetics, 2005Co-Authors: Dexin Wang, Jay Brown, Tim Hazelton, Jim DaughtonAbstract:Microchips of 360/spl deg/ angle sensors using spin Valve Materials were designed, fabricated, and tested with excellent performance. The spin Valve material used for the angle sensor has a structure of Ta-NiFeCo-CoFe-Cu-CoFe-Ru-CoFe-CrMnPt. External magnetic fields have little torque on the CoFe-Ru-CoFe structure up to at least 500Oe, which is the highest value available during the test. This is due to the strong antiparallel exchange coupling between the two CoFe sublayers of the same thickness via a thin layer of Ru and the resulting zero net magnetic moment. There is a sharp switching of the free layer with a low coercivity of 4 Oe along the easy axis. Both the high standoff field and small coercivity ensure that the sensor operates properly with large tolerance in mechanical assembly. The angle sensor is used stationary in combination with a disc-shaped permanent magnet attached to a rotating shaft near the sensor. The permanent magnet is magnetized in-plane, thus creating a field that is rotating with the shaft. The magnetic field from the permanent magnet forces the free layer magnetization to follow the field and rotate with it. With a fixed reference layer magnetization and an in-phase following of the free layer magnetization, the magnetoresistance is a simple cosine function of the angle between the rotating permanent magnet and the stationary sensor. A special Wheatstone-bridge with four spin Valve resistors is used to compensate the thermal drift expected in application environments. One half bridge has a 90/spl deg/ phase delay from the other, resulting in a cosine and a sine function, in combination to uniquely determine any angular relationship between the permanent magnet and the sensor between 0 to 360/spl deg/.
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Angle sensor using spin Valve with SAF structure
2005 IEEE International Magnetics Conference (INTERMAG), 2005Co-Authors: Dexin Wang, Jay Brown, Tim Hazelton, Jim DaughtonAbstract:An angle sensor using spin Valve Materials was designed, fabricated and tested. The spin Valve material, composed of a top-pinned synthetic antiferromagnet layer for better standoff fields and a composite free layer for low coercivity and high magnetoresistance, has a structure of Ta-NiFeCo-CoFe-Cu-CoFe-Ru-CoFe-CrMnPt. The spin Valve film showed switching of the free layer with low coercivity (5 Oe) and a plateau of the high field region (up to 500 Oe) after annealing at 250/spl deg/C for 1 hour. Two half-Wheatstone-bridges provide cosine and sine functions to uniquely determine angular positions between the angle sensor and a disc-shaped permanent magnet from 0 to 360 degrees at 2-6 mm airgap values.
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360° angle sensor using spin Valve Materials with SAF structure
IEEE Transactions on Magnetics, 2005Co-Authors: Dexin Wang, Jay Brown, Tim Hazelton, Jim DaughtonAbstract:Microchips of 360 degrees angle sensors using spin Valve Materials were\ndesigned, fabricated, and tested with excellent performance. The spin\nValve material used for the angle sensor has a structure of\nTa-NiFeCo-CoFe-Cu-CoFe-Ru-CoFe-CrMnPt. External magnetic fields have\nlittle torque on the CoFe-Ru-CoFe structure upto at least 500Oe, which\nis the highest value available during the test. This is due to the\nstrong antiparallel exchange coupling between the two CoFe sublayers of\nthe same thickness via a thin layer of Ru and the resulting zero net\nmagnetic moment. There is a sharp switching of the free layer with a\nlow coercivity of 4 Oe along the easy axis. Both the high standoff\nfield and small coercivity ensure that the sensor operates properly\nwith large tolerance in mechanical assembly. The angle sensor is used\nstationary in combination with a disc-shaped permanent magnet attached\nto a rotating shaft near the sensor. The permanent magnet is magnetized\nin-plane, thus creating a field that is rotating with the shaft. The\nmagnetic field from the permanent magnet forces the free layer\nmagnetization to follow the field and rotate with it. With a fixed\nreference layer magnetization and an in-phase following of the free\nlayer magnetization, the magnetoresistance is a simple cosine function\nof the angle between the rotating permanent magnet and the stationary\nsensor. A special Wheatstone-bridge with four spin Valve resistors is\nused to compensate the thermal drift expected in application\nenvironments. One half bridge has a 90 degrees phase delay from the\nother, resulting in a cosine and a sine function, in combination to\nuniquely determine any angular relationship between the permanent\nmagnet and the sensor between 0 to 360 degrees.
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360/spl deg/ angle sensor using spin Valve Materials with SAF structure
IEEE Transactions on Magnetics, 2005Co-Authors: Dexin Wang, Jay Brown, Tim Hazelton, Jim DaughtonAbstract:Microchips of 360/spl deg/ angle sensors using spin Valve Materials were designed, fabricated, and tested with excellent performance. The spin Valve material used for the angle sensor has a structure of Ta-NiFeCo-CoFe-Cu-CoFe-Ru-CoFe-CrMnPt. External magnetic fields have little torque on the CoFe-Ru-CoFe structure up to at least 500Oe, which is the highest value available during the test. This is due to the strong antiparallel exchange coupling between the two CoFe sublayers of the same thickness via a thin layer of Ru and the resulting zero net magnetic moment. There is a sharp switching of the free layer with a low coercivity of 4 Oe along the easy axis. Both the high standoff field and small coercivity ensure that the sensor operates properly with large tolerance in mechanical assembly. The angle sensor is used stationary in combination with a disc-shaped permanent magnet attached to a rotating shaft near the sensor. The permanent magnet is magnetized in-plane, thus creating a field that is rotating with the shaft. The magnetic field from the permanent magnet forces the free layer magnetization to follow the field and rotate with it. With a fixed reference layer magnetization and an in-phase following of the free layer magnetization, the magnetoresistance is a simple cosine function of the angle between the rotating permanent magnet and the stationary sensor. A special Wheatstone-bridge with four spin Valve resistors is used to compensate the thermal drift expected in application environments. One half bridge has a 90/spl deg/ phase delay from the other, resulting in a cosine and a sine function, in combination to uniquely determine any angular relationship between the permanent magnet and the sensor between 0 to 360/spl deg/.
