Influences Of Induced Anisotropy On The Piezomagnetic Effect In TbDyFe Oriented Crystals

As a gaint magnetistritive material, cubic Laves phase TbDyFe alloys can realize quick conversion between mechanical energy and electromagnetic energy. Due to the giant magnetostriction, high energy density, quick response, TbDyFe alloys could be widely applied in transducers, sensors, and actuators. Magnetic field annealing can change the initial magnetic domain distribution of TbDyFe oriented crystals, hence improve the magnetostrictive and piezomagnetic responses. In this work,<110> oriented Tb0.3Dy0.7Fe1.95 alloy rod was annealed at 500℃under a magnetic field of 0.3 T, which was applied 35°with respect to the rod axis.The evolution of magnetic domain configurations was studied with a magnetic force microscopy, the magnetostrictive and piezomagnetic responses were studied under a coupled magnetomechanical space, the mechanism of induced anisotropy by magnetic field annealing on the magnetostrictive and piezomagnetic performances was proposed. Main results are as follows:The magnetic field annealing can significantly enhance the magnetostrictive performance of <110> oriented Tb0.3Dy0.7Fe1.95 rod. After magnetic annealing, saturation axial magnetostrictionλs increased from 1023 to 1650 ppm without applying any pre-stress. When the compressive pre-stress was less than 20 MPa, the magnetically annealed specimen still exhibited obvious magnetostriction "jump" effect. Satisfactory magnetostriction as high as 2310 ppm was obtained with the application of 20 MPa compressive pre-stress. The forced magnetostrictive constant d33 was improved drastically indicating the enhancement of magnetostrictive performance under low magnetic fields and low compressive pre-stresses. We found that the movement of Non-1800 wall at low external fields was favored, which contributed to the improvement of magnetostrictive performance.The magnetic field annealing can also enhance remarkabely the piezomagnetic response of <110> oriented Tb0.3Dy0.7Fe1.95 alloy rod. After magnetic annealing, the magnetic induction under the compressive stress of 40 MPa was increased from 0.354 T to 0.43 T by 21.5%. The maximum piezomagnetic coefficient d33* was increased from 18.86×10-3 T/MPa to 19.92×10-3 T/MPa by 5.6%. In addition, the critical stress, under which piezomagnetic coefficient d33* reaches a maximum, was effectively reduced at zero bias magnetic field. However, the magnetic annealing results in a slight increase of the optimum bias magnetic field, at which maximum piezomagnetic coefficient d* 33 was obtained. Moreover, the critical stress corresponding to maximum d* 33 increased with the increase of bias magnetic field. The influence of induced anisotropy on the piezomagnetic effect was discussed, based on the domain rotation process under compressive stress and parallel magnetic field, respectively.