Susceptibility Measurements and Magnetic Ordering of Hexagonal FeGe

Abstract

The spin structure of the metallic hexagonal B 35 phase of FeGe has been studied by means of susceptibility and magnetization measurements. Below the Neel temperature TN = 411 K hexagonal FeGe is a uniaxial antiferromagnet with the spins parallel to the c-axis. In each c-plane all spins are ferromagnetically coupled with an exchange constant J0 ≈ 22 meV. The antiferromagnetic exchange constant between nearest neighbour and next nearest neighbour c-planes are J1 = -3.5 meV and J2 = -0.9 meV resp. in the molecular field model. Susceptibility and spin flop experiments indicate that the spins tilt away from the c-axis below 30 K. We suggest that the spins then form a double cone structure with a cone halfangle of 20° at 4.2 K. In the double cone the c-plane components have a turn angle in the vicinity of 180° between nearest neighbour planes, which implies absence of long range order. The result is in good agreement with Fermi surface calculations by Sundström (Physica Scripta, following paper), which show the existence of several spin density wave vectors between Q = 0.89 π/c and Q = 1.3 π/c calipering different parts of the Fermi surface in a direction parallel to the c-axis.

Ordered CoSn-type ternary phases in Co3Sn3−xGex

“…Generally for an intermetallic compound, especially for a good metal, it is expected that the electronic behavior is dominated by the band properties, with localized effects considered less important. Thus, while the magnetism of FeGe is often explained in the localized spin model for simplicity, it has been noted that a band model is just as explanatory, and that it is probably most appropriate to consider a combined model [7,23]. That is, the band model predicts the observed properties, but the localized model is a convenient way to picture the periodicity of the magnetism.…”

“…While CoSn is nonmagnetic down to at least 0.5 K [3], B35 FeGe and FeSn both have unusual magnetic properties [3][4][5][6][7][8][9]. The Fe spins in FeGe order ferromagnetically in the kagome plane below 410 K, aligned along the c axis, and are antiferromagnetically ordered between layers.…”

Magnetic Properties of the Hf$_{1 - x}$$R_{x}$Fe$_{6}$Ge$_{6}$ (${R}={\rm Gd}$ and Dy) Compounds

“…The magnetic structure of the iron sublattice consists of ferromagnetic hexagons with the antiferromagnetically coupled magnetic moments along the axis. The absence of coupling between both sublattices results from a net cancellation of the -Fe exchange at the rare-earth sites [4]. For some atoms, i.e., Ti, Zr, Nb [5], Yb [6], Ho [7], the low temperature magnetic structure exhibits some canting of the Fe magnetic moment from the axis, as in the parent compounds FeGe, while for Sc and Hf such canting has not been observed.…”

A study on the magnetic behaviour of polymorphic YbFe6Ge6

“…The magnetism of the FeGe basis has been the subject of extensive investigation over the past four decades. This work encompasses 57 Fe Mössbauer spectroscopy [8][9][10], magnetic measurements [11][12][13], neutron diffraction [14][15][16] and theoretical studies [17,18]. The Fe sublattice orders antiferromagnetically below 410 K with the Fe moments aligned along the hexagonal C-axis.…”