Anelastic and magnetic effects in Ni3Al at ultrasonic frequencies

The elastic constants and ultrasonic attenuation were measured as a function of temperature, magnetic field and frequency in a nickel-rich Ni3Al single crystal containing boron. The force constants between nearest neighbour and next nearest neighbour atoms were deduced from the data, together with the anisotropy factor and the Debye temperature. A paramagnetic to ferromagnetic transition was observed at around 84 K, which is not associated with cusp-like dips in the elastic constants and maxima in the attenuation. However, in the ferromagnetic state of the material (T < 84 K) the presence of an applied magnetic field is found to affect elastic constants and attenuation. The observed changes can be accounted for in terms of domain wall motions induced by the applied ultrasonic field. The presence of boron does not seem to be monitored by an evident ultrasonic effect below room temperature.