Ultrasonic Propagation in Nickel and Mn-Ferrite at High Magnetic Fields

Abstract

The velocity and attenuation of ultrasonic waves at magnetic fields, sufficiently high to produce magnetic saturation in nickel and Mn-ferrite, have been measured as a function of orientation, intensity of magnetic field, and ultrasonic frequency at room temperature. In the case of nickel, the change in ultrasonic velocity was inversely proporational to the applied magnetic field in the range from 5 to 20 kG; the ultrasonic attenuation coefficient also changed and showed a frequency dependence of the relaxation type \fracω⁄ω₀1+ω²⁄ω₀² in the range from 5 to 65 Mc/s. In the case of Mn-ferrite, it was found that the magnitude of the changes in ultrasonic velocity was almost the same as that in the case of nickel, but no attenuation change was observed within experimental error. All the observations can be explained by the theory based upon magneto-elastic coupling and eddy current loss.