Barkhausen discontinuities, nucleation, and pinning of domain walls in etched microparticles of SmCo5

A study has been made of the effects of etching on the magnetic hysteresis of single SmCo5 particles. It has been shown that the domain-wall nucleation and pinning fields are substantially increased by etching in 0.5% HNO3 for various times up to 6.5 min. After further etching, these fields decreased. The use of a vibrating-reed magnetometer has enabled the observation of individual Barkhausen discontinuities in the motion of the domain walls which in turn can be used to characterize the coercivities of individual particles.