Perpendicular susceptibility, magnetomechanical coupling and shear modulus in Tb.27Dy.73Fe2

We have measured the perpendicular magnetomechanical coupling, perpendicular susceptibility and shear modulus in polycrystalline Tb.27Dy.73Fe2by measuring the self-impedance of a cylinder (Wiedemann effect). We find: (1) the maximum value of the perpendicular coupling factor to be greater than .7, considerably higher than the parallel value of .55; (2) the perpendicular susceptibility to be greater than the parallel susceptibility except at zero field where they are equal; (3) a considerably softened shear modulus; (4) an anomalous increase in the skin depth in a narrow range of frequencies above resonance. We present a theory which describes the magnetoelastic behavior and the anomalous skin effect.