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Persistent URL http://purl.org/net/epubs/work/30058
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Record Id 30058
Title EuMn2Ge2 and EuMn2Si2 - Magnetic structures and valence transitions
Abstract The magnetic structures of 153EuMn2Ge2 and 153EuMn2Si2 have been determined by neutron diffraction measurements (?1.8–723 K). The Mn sublattices of both EuMn2Ge2 and EuMn2Si2 order antiferromagnetically [TN=667(9)K; space group I4?/m?m?m and TN=391(5)K; space group Ip4/m?m?m?, respectively] with no evidence for ordering of the Eu+2 ions in EuMn2Ge2 down to 1.5 K. EuMn2Si2 exhibits a thermally driven valence transition around Tv?527K with a pronounced increase in the unit cell volume of ?7% from the Eu3+ state at low temperatures (T<?150K) to an average valence state of ?2.5 at high temperatures (T>?600K). The valence-induced volume changes have been analyzed for the first time in terms of the interconfigurational fluctuation model with occupation probabilities for the Eu2+ state in EuMn2Si2 and the average Euval values found to agree well with our reanalysis of earlier 151EuMn2Si2 isomer shift data. The strength of the magnetic interaction for antiferromagnetic ordering of the Mn sublattice is decreased by ?10%–15% as a result of the change in the electronic configuration of EuMn2Si2.
Keywords ISIS 2004 , Physics , Crystal , Engineering
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Language English (EN)
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Journal Article Phys Rev B 69 (2004): 174432. doi:10.1103/PhysRevB.69.174432 2004