Stress dependence of magnetostrictions and strains in [111]-oriented single crystals of Terfenol-D

Single crystals of Tb0.27Dy0.73Fe2 were prepared successfully by the Czochralski (CZ) method using a magnetic levitation cold crucible first in this laboratory. The Lane x-ray technique and metallography verified its twin-free single crystalline perfection. Weidmanstatten precipitation (WSP) slightly exists in these specimens with WSP platelets parallel to the {111} planes of Terfenol-D. Saturation magnetostriction were measured along three principal crystallographic axes [111], [11(2) over bar] and [1(1) over bar0$] of single crystal Tb0.27Dy0.73Fe2 with magnetic field parallel and then perpendicular to the measuring direction, which gives an intrinsic magnetostriction lambda(111) = 1640 x 10(-6) for [111] easy axis. Stress dependence of magnetostrictions and strains measured along three mutually perpendicular axes, [111], [11(2) over bar], and, [1(1) over bar0$] on [111]-oriented single crystalline rods of Terfenol-D indicates that apparent magnetostriction for [111] direction increases with increasing applied compressive stress along the rod axis, and reaches 2375 x 10(-6) under a stress of 24 MPa and a magnetic field of 20 kOe. Maximum d(33) decreases with the increment of applied stresses and the amount of WSP, and ranges from 1 x 10(-6)/Oe to 6 x 10(-6)/Oe at about 500 Oe. Less hysteresis appears. Magnetizing processes are calculated and compared with the measured changes of magnetostriction. The authors conclude that [111]-oriented single crystal of Terfenol-D is suitable for precise displacement actuators although it would be much better to eliminate the WSP precipitation. (C) 1996 American Institute of Physics.