Migaku Takahashi1, Hitoshi Saito1, Keiichi Takakura2, Terunobu Miyazaki2, Tokuo Wakiyama1 and Minoru Takahashi2
1Department of Electronics, Faculty of Engineering, Tohoku University, Sendai
Structure analysis by X-ray diffraction and precise metallographic observations by SEM were made for rapidly quenched Sm-Co alloy ribbons. The high temperature phase of Sm2Co17 compound was found in the composition range between 10 and 16 at%Sm. The SmCo5 phase was found in the Sm concentration above 16 at%Sm. According to observation results on the metallographic structure, the columnar structure in which c-axis was aligned parallel to the ejected direction of the ribbons was present in the ribbons fabricated at the relatively low roll velocity VR below 18 m/s. In the ribbons fabricated at the higher roll velocity VR>18 m/s, any columnar structure was absent, and only homogeneous spherical fine particles with random orientation of c-axis were present. The origin of the change in the coercive force iHc and the residual magnetization Mr with the roll velocity was discussed in connection with the change in the metallographic structure of the ribbons. As a result, the following were clarified: (1) The magnetization reversal process for the ribbons consisting of SmCo5 phase is ruled by the irreversible movement of 180°ree walls. (2) Increment of iHc and the decrement of Mr with increasing roll velocity on fabrication are caused by the decrease of the degree of c-axis orientation of grains and also by the structure change from the columns to fine spherical particles with random orientation. (3) iHc for the columns about 2 μ m in diameter is nearly the same as that of the spherical fine particles with the single domain structure, even though the multidomain structure is realized in the columns.
samarium-cobalt alloys, rapidly quenching, magnetic properties, structural properties, magnetic domain structure, magnetization reversal
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