Regensburg 2010 – scientific programme
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MA: Fachverband Magnetismus
MA 27: Spin Structures and Magnetic Phase Transitions
MA 27.1: Talk
Thursday, March 25, 2010, 17:15–17:30, H10
A scheme to calculate the Curie temperature for systems with induced magnetic moments with application to Co-Pt and Fe-Pd alloys — •Svitlana Polesya1, Sergiy Mankovsky1, Ondrej Sipr2, Christoph Strunk3, and Hubert Ebert1 — 1LMU Munchen, Dept. Physikalische Chemie, Butenandtstraße 11, D-81377 München — 2Institute of Physics Acad. of Science, Prague, Czech Republic — 3Institute for Exper. and Appl. Physics, University of Regensburg, Germany
The importance of including induced magnetic moments when calculating the Curie temperature of transition metal systems is shown for Pd-rich Fe-Pd alloys and Co-Pt alloys. For this binary alloys the components exhibit a different type of magnetism, i.e. spontaneous and induced. The finite temperature magnetic properties of these alloys are described using a generalised Heisenberg Hamiltonian that allows to account for the longitudinal fluctuation of induced moments of the Pd and Pt atoms. In Fe-Pd alloys with small Fe concentration the role of effective Fe-Fe interaction mediated by the induced Pd moments is crucial for the creation of ferromagnetic (FM) order. The Curie temperature Tc obtained for these alloys are in good agreement with experiment for the Fe concentration up to 15%. For the Co-Pt alloys the improvement of the Tc values with inclusion of the induced moments on Pt atoms is shown for the whole considered concentration range. The FM order in the ordered CoPt3 alloy that is observed experimentally is only possible due to the FM coupling to induced Pt moments while Co-Co coupling is primarily anti-ferromagnetic.