A Coil-free dc magnetic sensor utilizing magneto-mechanical damping in giant magnetostrictive material

A magnetoelectric (ME) laminate composite is fabricated by sandwiching one longitudinally magnetized Tb_0.3Dy_0.7Fe_1.92 (Terfenol-D) magnetostrictive layer between two transversely polarized Pb(Zr,Ti)O₃ (PZT) piezoelectric layers. This composite is quite sensitive to a small dc magnetic field variation (ΔH_dc). Due to magneto-mechanical damping of Terfenol-D, the output voltage decreases as H_bias increases. The correlation between H_bias and magneto-mechanical damping coefficient is analyzed theoretically from the aspect of energy consumption, which accounting for the output voltage correlated reversely proportional to H_bias. The experimental results show that measured voltage has a linear relationship to the applied small dc magnetic field, and the sensitivity limit is 2.64×10^-8T under resonance drive. These performances make the composite to be a promising material for coil-free dc magnetic field detection device. In comparison with previously reported traditional magnetic field sensors, the proposed architecture has: (i) avoiding to use the copper-coil as excitation source; (ii) taking advantage of the magneto-mechnical damping of Terfenol-D which is strongly dependent on H_bias; (iii) an ability to detect dc or quasi-dc magnetic field.