MFC (Magnetic Flux Concentrator) is located around the sensor to guide the magnetic field and concentrate it on the sensor. This research developed MFC which thickness doesn’t exceed few micrometers and low hysteresis. The optimized value of the distance between the MFC poles was determined by magnetic simulation. Research has propose structures with small coercivity of MFC. Single-layer (Ta/NiFe/Ta) MFC, bilayer (Ta/NiFe/IrMn/Ta) MFC and trilayer ((Ta/NiFe/Cu/IrMn)n/Ta) MFC are compared. Significant reduction in coercivity has been demonstrated for both bilayer and trilayer MFC compared to single-layer MFC. In order to enhance the amplification factor, trilayer structure was repeated several times to increase the ferromagnetic layer thickness, and the effect of the number of repetitions was investigated.
Table Of Contents
I. Introduction 1 II. Theoretical Background 3 2.1 Sensitivity amplification by MFC 3 2.2 Exchange bias 6 III. Experimental Methods 8 3.1 Design of the MFC pattern 8 3.2 Fabrication of thin film pattern 8 3.3 Magnetoresistance measurement 14 3.4 VSM (Vibrating Sample Magnetometer) 15 IV. Result & Discussion 16 4.1 Design of the MFC pattern 16 4.1.1 Optimization of the distance between the MFC poles 16 4.1.2 MFC pattern for single-ring sensor 18 4.2 Optimization of the MFC structure 20 4.2.1 Single-layer MFC 21 4.2.2 Bilayer MFC 22 4.2.3 Trilayer MFC 24 4.3 Total output voltage change of the sensor signal with MFC 26 V. Conclusion 28 References 29 Summary 31