Effects of spin fluctuations and anomalous thermal expansion of delta-Pu

TitleEffects of spin fluctuations and anomalous thermal expansion of delta-Pu
Publication TypeJournal Article
Year of Publication2010
AuthorsSolontsov A, Antropov VP
Journal TitlePhysical Review B
Date Published06/02
ISBN Number1098-0121
Accession NumberISI:000278300700003
KeywordsCERIUM, electronic-structure, magnetism, PLUTONIUM, state

We suggest a model for the magnetic dynamics of delta plutonium and its alloys in order to show that the dynamical fluctuations of the magnetization density, or spin fluctuations, may be responsible for the anomalies of their observed thermal expansion. We show that due to strong magnetoelastic coupling, spin fluctuations may essentially contribute to the volume strain by giving a negative magnetovolume contribution that is proportional to the squared local magnetic moment and the magnetic Gruneisen constant which is negative in delta plutonium. In the presented model, the local magnetic moment increases as the temperature rises, resulting in the interplay between the positive contributions to the volume strain from the lattice and the negative contribution from spin fluctuations, and finally leads to the Invar anomaly or to the negative coefficient of thermal expansion. Our results agree closely with the measured thermal-expansion data for Pu-Ga alloys.

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