Dynamic Magnetomechanical Behavior of Tb<italic>x</italic>Dy1–<italic>x</italic>Fe<italic>y</italic>Alloy Under Small-Signal AC Drive Fields Superposed With Various Bias Fields

Abstract

The small-signal vibration model of Tb x Dy1– x Fe y plate was developed by mechanical-electrical analogy method. Based on the model, we demonstrated the reasonableness of measuring the small-signal magnetomechanical behaviors by a laser Doppler vibrometer. The strain coefficient of the Tb x Dy1– x Fe y plates was measured as a function of frequency and bias field ( $H_{\mathrm{ dc}})$ , and Young’s modulus, mechanical quality factor ( $Q_{m})$ , relative permeability, and magnetomechanical coupling coefficient were investigated as a function of $H_{\mathrm{ dc}}$ . Many novel characteristics were observed under the drive of a small-signal field (7.96 A/m). The change tendency of the strain coefficient at resonance differs from that at low frequency, and the resonant strain coefficients are significantly high (>85 nm/A) in a wide range of bias field from 4.78 to 55.72 kA/m. Both the negative- $\Delta E$ and positive- $\Delta E$ effects are observed, and the negative- $\Delta E$ effect in the low field range is also remarkable. In particular, $Q_{m}$ sharply decreases from the initial value of 104 to a minimum value of 11.4 and, then, increases slowly, and the ratio of the maximum variation of $Q_{m}$ over $H_{\mathrm{ dc}}$ to the minimum value of $Q_{m}$ exceeds $\sim 812.3$ %. This is an important systematic investigation on the small-signal dynamic magnetomechanical behavior of Tb x Dy1– x Fe y , and the results are highly beneficial to the designing of magnetostrictive devices.