Domain wall grooving in R-Co magnet materials

When rare earth (R) cobalt alloys such as SmCo5and MMCo5were mechanically polished for microscopic examination, it was noted that grooves are formed at the domain walls present in the material. "Grooving" was also found at the domain walls when RCo5alloy specimens were electropolished. Light microscope and scanning electron microscope were used to observe the grooves. The grooves are interpreted as resulting from accelerated material removal at the domain walls compared to the material removal in the rest of the specimen during the polishing (mechanical, chemical, or electrochemical) operation. Domain wall energies in RCo5compounds are in the range of 50 to 100 erg/cm2compared to about 0.5 to 1 kerg/cm2for the surface energy of the alloys. The grooving of the domain walls is discussed in light of those relative energy differences.