Structure and magnetic properties of the ThMn/sub 12/ type NdFeM alloys (M=Si/Al/B/transition metals)

Thirteen Nd(Fe,M)/sub 12/ alloys were studied, where M=Si, Al, B, Ti, V, Cr, Mn, Zr, Hf, Nb, W, Mo, or Ta. Those containing Si, Ti, V, Cr, Mn, Mo, or W are tetragonal ThMn/sub 12/ (1-12 for short) type structures. For the other alloys, the existence of Fe/sub 3/M, Fe/sub 2/M, FeM, and/or FeM/sub 2/ phases has been evidenced by X-ray diffraction (XRD). The size of the M atom is found to be crucial in determining its ability to stabilize the 1-12 phase. In NdFe/sub 12-x/Ti/sub x/ alloys, the 1-12 phase exists in a wide range of x values from 0.7-2.0; however, the Fe/sub 2/Ti phase appears when x exceeds 1.0. Hence, NdFe/sub 11/Ti is probably not a line compound. For the other alloys with 1-12 phase, only x=2 was examined. The c/a value remains invariant at 0.558 to 0.559 when M is a transition metal, and equals 0.564 for M=Si. The Curie temperatures of these alloys, in decreasing order, are 310 degrees C, 301 degrees C, 278 degrees C, 270 degrees C, 252 degrees C, 195 degrees C, and 119 degrees C for V, Si, Ti, Cr, W, Mo, and Mn, respectively. For the alloy with Ti, x=1, whereas for the others x=2. The anisotropy field for these alloys, measured for aligned polycrystalline powder at room temperature, is low; the maximum value is 26.8 kOe for NdFe/sub 11/Ti, which increases to 54.5 kOe at 4.2 K.<
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