Magnetic domain structure and temperature dependence of coercivity in Sm(CobalFe0.1Cu0.1Zr0.033)z (z=6.8, 7.4) magnets

The magnetic domain structure and temperature dependence of coercivity of Sm(CobalFe0.1Cu0.1Zr0.033)z (z=6.8, 7.4) magnets, quenched at 400 °C, 600 °C and 810 °C in the aging process, have been investigated. For the two kinds of magnets Sm(CobalFe0.1Cu0.1Zr0.033)z (z=6.8, 7.4), with the increase of quenching temperature, the domain structure becomes coarser, leading to the abnormal temperature dependence of coercivity that means the coercivity increases with the increasing temperature in a certain temperature range. Moreover, for higher z value magnets, such as z=7.4, compared to z=6.8, the domain structure tends to show narrower and more additional domain, and the abnormal temperature dependence of coercivity requires a higher quenching temperature. A big gradient of Cu in the 1:5 cell boundary phase is suggested to form more easily in the higher z value magnets, resulting in the decrease of the tendency of anomalous temperature dependence of coercivity, accounting to the non-continuous domain wall model.