Dynamic Magnetomechanical Behavior of TbxDy1–xFey Alloy Under Small-Signal AC Drive Fields Superposed With Various Bias Fields

The small-signal vibration model of Tb
_x
Dy
_1-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
Dy
_1-x
Fe
_y
plates was measured as a function of frequency and bias field (Hdc), and Young's modulus, mechanical quality factor (Qm), relative permeability, and magnetomechanical coupling coefficient were investigated as a function of Hdc. 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-AE and positive-AE effects are observed, and the negative-AE effect in the low field range is also remarkable. In particular, Qm 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 Qm over Hdc to the minimum value of Qm exceeds ~812.3%. This is an important systematic investigation on the small-signal dynamic magnetomechanical behavior of Tb
_x
Dy
_1-x
Fe
_y
, and the results are highly beneficial to the designing of magnetostrictive devices.