New Developments on the Invar-Effect
1989; IOP Publishing; Volume: T25; Linguagem: Inglês
10.1088/0031-8949/1989/t25/038
ISSN1402-4896
Autores Tópico(s)Magnetic Properties of Alloys
ResumoWe briefly review the history of the Invar-effect and present experimental data on the Invar behavior of FeNiMn, Fe3Pt and amorphous FeB alloys, clearly demonstrating that neither magnetic (or metallurgical) inhomogeneities nor weak itineracy are the origin of the Invar-effect, as believed for a long time. Instead, we will demonstrate that recent band calculations within the local spin density approximation can form the basis for a principally new understanding of the Invar-effect. Although the volume instabilities of the magnetic moments of certain but Invar typical 3d-elements are observed at T = 0 within these models, we will give direct experimental evidence for the occurrence of high spin-low spin state transitions with temperature in ordered Fe3Pt. Finally, we analyze high temperature data of the specific heat and thermal expansion anomalies in different Invar systems. The results give further support for the idea that the broad spectrum of Invar anomalies is caused by thermal exitation of certain energy levels within the instability range of the 3d-moments.
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