MAGNETIC-PROPERTIES OF SM2FE17CX COMPOUNDS

A systematic investigation of the magnetic and structural properties of as-cast Sm2Fe17C(x) compounds with 0 less-than-or-equal-to x less-than-or-equal-to 1.5 has been made with x-ray diffraction, thermomagnetic analysis, and superconducting quantum interference device magnetometry. Crystal structure studies have shown that the ternary carbides form a rhombohedral Th2Zn17-type structure. The lattice constants at room temperature increase with x, indicating that carbon substitutes interstitially. The Curie temperature increases strongly with x from T(C) = 130-degrees-C for x = 0 to 247-degrees-C for x = 1.5. The introduction of interstitial carbon atoms into the 2:17 structure leads to a dramatic change in the magnetic anisotropy of Sm2Fe17C(x) compounds. The value of K1 increases with increasing x, and a transition from an "easy-plane" to an "easy-axis" anisotropy takes place.