Magnetische Eigenschaften der ternären Phase (Fe x Ni1-x )11Se8

The partial substitution of nickel by iron in the body centered tetragonal crystal structure of the ternary compound (Fe _x Ni_1–x )₁₁Se₈ is restricted to the range of 0.04<x<0.23 at 580°C. The magnetic properties of samples with different compositions were studied by susceptibility measurements in the temperature region from 100 to 300 K. The continuous addition of Fe atoms resulted in a decreasing temperature dependence of the magnetic susceptibilities. Only for compositions withx0.14 an approximatedCurie—Weiss behaviour was observed. The Fe-rich samples (x>0.14) showed a very high constant paramagnetism which could not be interpreted asPauli paramagnetism. The evaluation of magnetic moments was based on the assumption that only the Fe atoms contribute to the temperature dependence of the magnetic susceptibilities. The actual value of the magnetic moments is supposed to be affected by magnetic interactions between neighbouring Fe atoms. The extrapolation of the magnetic moments towardsx=0 is compatible with a magnetic moment of 3.87 _B corresponding to three unpaired d-electrons per Fe atom. According to the negativeWeiss constants derived fromCurie—Weiss law antiferromagnetic interactions at low temperatures can be expected.

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