Anisotropic magnetostriction in Tb0.27Dy0.73Fe1.95

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Abstract
The magnetostriction of a single crystal of Tb0.27Dy0.73Fe1.95 grown by the Bridgman technique was measured over the temperature range of magnetic anisotropy compensation (300–330 K). Using a growth rate of 3 cm/h, twinned dendrites were suppressed. We looked for, but found no evidence of, modification of the cubic structure by the resulting cellular [112] growth. Magnetostriction measurements along all four 〈111〉 axis are nearly identical. However, the magnetostriction is highly anisotropic, with λ100/λ111=0.06±0.02 at 300 K. The effects of this large magnetostriction anistropy are discussed. Of particular importance is the magnetostriction along nonprincipal axes. Here we find that the magnetization direction for maximum strain is not collinear with the strain measurement direction. Measurements along the growth [112̄] direction revealed the maximum magnetostriction with the magnetization 14.75° from [112̄]. Expressions which relate the direction of magnetization for maximum strain to the measurement direction are derived for magnetization rotation in the (110) and (100) planes. The existence of noncollinear maximum magnetostriction axes leads to a region of 180° domain wall motion near H=0 in transducer rods of Tb0.27Dy0.73Fe1.95 under compressive prestress. This portion of the magnetization curve is not accompanied by magnetostriction. Magnetostriction curves in nonsaturating magnetic fields also provide a method to determine the magnetic anistropy. Anisotropy constants calculated in this way are compared to those determined earlier by torque and magnetization measurements.

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