Das magnetische Verhalten von FeGe₂-Einkristallen, auch für Abweichungen von der stöchiometrischen Zusammensetzung

Abstract

Tetragonal stoichiometric pure FeGe₂ single crystals are para- or antiferro-magnetic with an isotropic mass susceptibilityε ₃₀₀=6.5·10⁻⁶ cgs _m and Δ(1/χ)/ΔT=150 between 90 and 435 °K. Deviations from the stoichiometry give on the germaniumside a corresponding decrease ofχ. Excess iron risesχ and aboveΔFe=+2% a drastic field- and temperature-dependence ofχ sets in. Crystals with nonstoichiometric overall composition (by chemical analysis) are made up of two phases: In a matrix of pure FeGe₂ precipitates lie parallel to thec-axis, as revealed by polishing and etching. This behaviour explains that Mössbauer experiments give no variation of the Néel point with composition. The precipitates make the iron rich crystals magnetically anisotropic.