Two parent alloys with compositions Mn11Ge8 and Mn3Ge2 were prepared by melting at 1273 K for 3.6 × 103 s (1 h) in an argon atmosphere. The alloys were then annealed at 953 K for 9.0 × 105 s (250 h) in an evacuated quartz tube. The annealed Mn11Ge8 alloy is not single phase but a two-phase with free germanium. In order to establish the composition of the most germanium-rich germanide, using the two parent alloys, sintered MnGex with the compositions in the range 0.664 ≤ x ≤ 0.753 were prepared by a powder metallurgical technique. The apparent density, resistivity and magnetization of MnGex changed drastically over the very narrow range 0.700 ≤ x ≤ 0.706. From the results of X-ray integrated diffraction intensity measurements and quantitative analyses by means of electron probe micro-analysis and pycnometric density, it is confirmed that the most germanium-rich germanide of manganese is a line compound Mn44Ge31.
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