Highly coercive melt-spun Sm(Co,Fe,Cu,Zr)z magnets prepared by simple processing

A systematic study has been undertaken to understand the effect of temperature range for the cooling regime on microstructure and magnetic properties at both room and high temperatures of melt-spun Sm(Co,Fe,Cu,Zr)_z ribbons. It was found that the coercivity of ribbons at room temperature depends strongly on the quenching temperature. A coercivity of 3 T as well as uniform cellular and lamellar microstructure were obtained for Sm(Co_0.74Fe_0.1Cu_0.12Zr_0.04)_7.5 by simple processing: preparation of as-spun ribbons at 5 m/s, aging at 850°C for 3 h, subsequent slow cooling to 400°C and quenching. Higher quenching temperature leads to lower coercivity at room temperature but smaller temperature coefficients and even positive ones were obtained in the ribbons quenched above 750°C, which is due to the low Cu content in the 1:5 cell boundary phase at this stage. The lower the quenching temperature, the more negative the temperature coefficient and a coercivity of 0.83 T at 400°C was obtained in the sample quenched at 600°C. The different temperature coefficients are discussed in terms of a domain wall pinning model.