Berlin 2008 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 32: Postersession II: Spinstruct./Phase Trans. (1-10); Spinelectronics (11-15); Thin Films (16 - 36); Particles/Clusters (37-45); Multiferroics (46-54); Spindynamics/Spin Torque (55 - 76); Post Deadlines (77-79)

MA 32.6: Poster

Freitag, 29. Februar 2008, 11:15–14:00, Poster E

Longitudinal fluctuations in itinerant-electron systems — •Leonid Sandratskii — Max Planck Institute of Microstructure Physics, Halle, Germany

The recent successes in the understanding of the thermodynamics of the itinerant-electron systems are to a large extent related to the so-called adiabatic treatment of the atomic moments. This concept allows to introduce disorder of the atomic moments within the itinerant-electron picture and solves the problems of the Stoner model. A most used mathematical approach is the mapping of the itinerant-electron system on a Heisenberg-type Hamiltonian with subsequent application of a statistical-mechanics scheme to evaluate the temperature dependence of the magnetization and the Curie temperature.

Despite important successes with respect to the Stoner theory it becomes increasingly clear that many physical effects in the itinerant magnets cannot be described, even on the qualitative level, without taking into account the longitudinal fluctuations of the atomic moments in addition to the transversal fluctuations described by the Heisenberg-type Hamiltonians. The examples of such effects are the short range magnetic order in Ni above the Curie temperature or metamagnetic order-order phase transition in FeRh. Another important physical problem is the relation between longitudinal magnetic fluctuations and half-metalicity.

In this presentation we will report on recent studies of the role of the longitudinal fluctuations in itinerant-electron systems.