Magnetic Spin Valve Sensors with Different Geometry to Magnetic Bead Detection for Biosensor Application
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1032-I14-37
Magnetic Spin Valve Sensors with Different Geometry to Magnetic Bead Detection for Biosensor Application Jeong Dae Suh, and Myung Ae Chung Medical Information Convergence Team, Electronics and Telecommunications Research Institute, 138 Gajeongno, Daejeon, 305-350, Korea, Republic of ABSTRACT We have demonstrated the use of highly sensitive spin valve sensors for the detection of micron magnetic beads. By using a ring shape, cross shape, and meander line shape sensors, we were able to detect the presence of 2.8 µm size magnetic beads in real time by direct measurement of magnetic dipole fields from magnetic beads. The sensitivity of the ring, cross and meander line sensors were obtained about 50 µV/Oe, 7 µV/Oe, 30 µV/Oe and sensor output signals of 50 µV , 30 µV, 90 µV were obtained in an external applied field of 10 Oe and 1 mA sense current. Our results shows that ring, cross, and meander line shape spin valve sensors are very promising candidates for the detection of biomolecules with magnetic labels.
INTRODUCTION Magnetic (spintronic) sensors are used in a variety of spintronic devices as read head sensors, magnetic memory, and magnetic biosensors. During the last few years, magnetoresistive (MR) sensors have been intensively studied for the detection of magnetic stray field for biomolecules detection, an effect that is attributed to change the MR sensor output signal voltage change. In the MR sensor based biological applications, the detection of magnetic bead is one of the key issues. Several on chip MR sensors such as giant magnetoresistance (GMR) sensors [13] and spin valve (SV) sensors [4-7] with strip line geometries have been demonstrated as a biosensor for biomolecules detection. In addition, as an alternative MR strip line sensors, anisotropic magnetoresistance (AMR) based ring shape sensor [8] and AMR based cross shape sensor (planar hall sensor) [9,10] have been proposed. However there has been no work reported yet on the magnetic bead detection in ring, cross, and meander line shape MR sensors based on spin valve structures. Generally it is known that spin valve sensor offer more higher sensitivity in detection of magnetic beads than GMR or AMR sensors. In this paper, we report the high sensitive spin valve sensors with a ring, cross, and meander line shape geometries for detecting magnetic beads as potential biosensor applications.
EXPERIMENT Spin valve(SV) films used in this study had the structure of Ta(5nm)/NiFe(6 nm)/Cu(3 nm)/NiFe(3 nm)/IrMn(15 nm)/Ta(5 nm). They were deposited onto oxidized Si (100) substrate by DC magnetron sputtering under 3 mTorr argon pressure, in a system with a base pressure below 10-7 Torr at room temperature. During growth of exchange-biased thin film layer, an in-
situ field of 300 Oe was applied paralled to the plane of thin films, which imposed an exchange pinning axis along the field direction. Magnetic sensors were fabricated by standard optical lithography and ion beam milling method. SV films were patterned into ring shapes of 18 µm outer diameter
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