Control of chirality of transition-metal monosilicides by the Czochralski method


The crystallographic and magnetic chirality of the B20 (space group P213) solid solutions Fe1−xCoxSi and pure MnSi grown by the Czochralski method has been studied by means of the single crystal x-ray diffraction and the small-angle diffraction of polarized neutrons. To test the possibilities to control the crystal handedness, first, we have grown a series of MnSi crystals and one series of Fe1−xCoxSi samples with x=0,0.10,0.15,0.20,0.25,0.30,0.50 using a right-handed crystal as a seed. Second, we have grown another series of MnSi and Fe1−xCoxSi samples again of different concentrations using a left-handed crystal as a seed. In 90% of the cases the grown sample has been found to be enantiopure and to inherit the crystallographic chirality of its seed crystal. In 10% of the cases undefined circumstances flip the chirality over for the next progeny or produce a racemic sample. The magnetic chirality of these compounds has been shown to be rigorously related to their crystallographic handedness, but in the opposite way for MnSi and for Fe1−xCoxSi.
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