La structure magnetique de FeGe monoclinique a ete determinee par diffraction des neutrons. Entre TN = 342 K et Tc = 115 K, la structure se caracterise par l'existence de plans a peu pres ferromagnetiques, couples antiferromagnetiquement, alors que les moments des atomes de fer situes entre ces plans ne sont pas ordonnes. Ils s'ordonnent a Tc. Pour T < Tc, la structure presente un arrangement conique a longue periode (≈ 395 A). Les resultats de spectrometrie Mossbauer sont compatibles avec ceux de diffraction neutronique.



The magnetic structure of monoclinic FeGe is determined by neutron diffraction. Between TN = 342 K and Tc = 115 K, the magnetic structure is characterized by nearly ferromagnetic planes, antiferromagnetically coupled, while the magnetic moments of iron atoms located between these planes are not ordered. They order magnetically at Tc. For T < Tc, the iron moments form a coned structure with a periodicity of ≈ 395 A. The Mossbauer spectroscopy results are consistent with those of neutron diffraction.

Structures magnétiques de FeGe monoclinique

Mossbauer spectroscopy of Co germanides proves the existence of three stoichiometric phases: CoGe2, CoGe, and Co2Ge. The isomer shift values of these phases indicate covalent bonds between (Co)Fe and Ge. No magnetic ordering is observed down to 4.2 K. 57Co diffused in Ge results in a segregated phase, the Mossbauer parameters of which differ from the values of the stoichiometric compounds. The spectra of implanted samples indicate the existence of Co in a highly symmetric position (possibly tetrahedral) and at defect sites. Thermal annealing results in the same segregated phase as observed after Co diffusion.



In Kobaltgermaniden konnen mosbauerspektroskopisch drei Phasen identifiziert werden: CoGe2, GoGe und Co2Ge. Die gemessenen Isomerieverschiebungen dieser Phasen lassen auf kovalente Bindungen zwischen (Co)Fe and Ge schliesen. Bis zu Temperaturen von 4,2 K wird kein magnetischer Ordnungsvorgang beobachtet. Diffusion von 57Co in eine Ge-Matrix resultiert in einer Ausscheidungsphase, deren Mosbauerparameter von den Parametern der stochiometrischen Zusammensetzung verschieden sind. Spektren von implantierten Proben zeigen Co auf hochsymmetrischen Gitterplatzen (moglicherweise Tetraeder) und auf niedersymmetrischen Defektplatzen. Nach Auslagerung der Proben entsteht dieselbe Ausscheidungsphase, wie sie nach der Eindiffusion von Co in Ge beobachtet wird.

Cobalt–germanium structures investigated by mössbauer spectroscopy

Domaines d'existence et proprietes magnetiques des germaniures ternaires monocliniques Fe1−xCoxGe et Fe1−xNixGe

Intricate magnetic behavior of Fe6Ge5 and its origin within a complex iron framework: The magnetic and 57Fe Mössbauer study

The Mossbauer spectra of Fe 57 in FeGe were measured over the temperature range from 79°K to 413°K. The hyperfine field due to the antiferro-magnetic ordering was observed. Its value at 79°K was 155 kOe. The Neel point as determined from the temperature dependence of the internal magnetic field was 400°K. The isomer shift at room temperature was +0.22 mm/s. relative to pure Fe and varied with temperature like that of Fe. The electric quadrupole splitting \(\frac{1}{2}e^{2}qQ\) was +0.35 mm/sec at room temperature.

C. Max

Papers

Etude des propriétés magnétiques de la variété monoclinique du monogermaniure de fer