The Electrical Resistivity of Hexagonal FeGe Single Crystals

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Abstract
Electrical resistivity measurements have been carried out on hexagonal FeGe (B 35), which is a uniaxial antiferromagnet with TN=411 K. The resistivity parallel to the c-axis exhibits a hump below TN, which arises from the magnetic superzones cutting and distorting different contributions to the Fermi surface. For the current in the basal plane a mere change in slope is observed in the resistivity at the Néel temperature. Critical scattering, as well as imperfections, tend to smooth out the transition behaviour and an attempt is made to determine the critical exponent in d/dT = Cε-λ, where ε = |T-TN|/TN. For current parallel to the c-axis λ ≈ 0.8 for T>TN and λ ≈ -0.4 for T<TN. The case of resistivity perpendicular to the c-axis is less amenable to detailed analysis. The strong ferromagnetic ordering in the basal plane gives rise to long-range spin fluctuations, while the weak antiferromagnetic interactions along the c-axis give mainly short-range fluctuations above TN.