Ultrasonic Attenuation at the Magnetic-Phase Transition in Gadolinium

Abstract
We present ultrasonic attenuation measurements in the vicinity of the Curie temperature. Longitudinal waves along the c axis exhibit a large critical attenuation, whereas transverse waves show only a spurious attenuation peak. Along the a axis the critical attenuation for longitudinal waves is much smaller. In a nonsymmetry direction both longitudinal and transverse waves show large critical attenuation. AH these results can be explained, assuming the spin-phonon coupling is of the volume magnetostrictive type. For longitudinal waves propagating either along the c or a axis we find the following attenuation law for (T − TC)/TC > 1×10−3 α ∝ ω2(T − TC)−1.2.

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