Invar, AF-Invar, Anti-Invar and Martensite in FCC Fe-Based Alloys : An Attempt to Order this Chaos
E.F. Wassermann and P. Entel
Experimentelle und Theoretische Tiefemperaturphysik und SFB 166, Gerhard-Mercator Universitat, 47048 Duisburg, Germany
Abstract.
Systematics concerning magnetic and structural phase transitions within Fe-based sytems can be achieved if experimental data are analyzed as a function of composition and the atomic volume. The findings can be understood from calculations of the exchange coupling of pure fcc Fe as a function of the n.n. distance. Decisive is that the volume increase going along with Invar, AF-Invar, Anti-Invar as well as martensite transitions originates from a charge transfer between antibonding electronic orbitals with $g symmetry and AF exchange to non-bonding orbitals with eg symmetry and FM exchange. Which of the effects is leading at a given composition is a question of the position of the Fermi energy relative to these electronic levels. The question of how an effect manifests itself as a function of temperature is a question of the different strength of the $g- and eg-electron-phonon coupling.
https://hal.archives-ouvertes.fr/jpa-00254089/document
Experimentelle und Theoretische Tiefemperaturphysik und SFB 166, Gerhard-Mercator Universitat, 47048 Duisburg, Germany
Abstract.
Systematics concerning magnetic and structural phase transitions within Fe-based sytems can be achieved if experimental data are analyzed as a function of composition and the atomic volume. The findings can be understood from calculations of the exchange coupling of pure fcc Fe as a function of the n.n. distance. Decisive is that the volume increase going along with Invar, AF-Invar, Anti-Invar as well as martensite transitions originates from a charge transfer between antibonding electronic orbitals with $g symmetry and AF exchange to non-bonding orbitals with eg symmetry and FM exchange. Which of the effects is leading at a given composition is a question of the position of the Fermi energy relative to these electronic levels. The question of how an effect manifests itself as a function of temperature is a question of the different strength of the $g- and eg-electron-phonon coupling.
https://hal.archives-ouvertes.fr/jpa-00254089/document
Hello, my name is Dr Abderrahmane Reggad. I'm a 51 year old and I am a researcher in materials' sciences. 
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