Berlin 2008 – wissenschaftliches Programm

Bereiche | Tage | Auswahl | Suche | Downloads | Hilfe

MA: Fachverband Magnetismus

MA 2: Micro and Nanostructured Magnetic Materials I

MA 2.10: Vortrag

Montag, 25. Februar 2008, 12:30–12:45, EB 301

Ion irradiation induced local creation of ferromagnetism in Fe₆₀Al₄₀ alloys — •T. Strache¹, M. O. Liedke¹, J. Fassbender¹, W. Möller¹, E. Menendez², J. Sort^2,3, T. Gemming⁴, A. Weber⁵, L. J. Heyderman⁵, K. V. Rao⁶, S. C. Deevi⁷, and J. Nogues^3,8 — ¹Forschungszentrum Dresden-Rossendorf, Germany — ²Universitat Autonoma de Barcelona, Spain — ³ICREA Barcelona, Spain — ⁴IFW Dresden, Germany — ⁵PSI Villigen, Switzerland — ⁶Royal Institute of Technology, Stockholm, Sweden — ⁷Research Center Philip Morris, Richmond, USA — ⁸Institut Catala de Nanotecnologia, Spain

Ion irradiation of Fe₆₀Al₄₀ alloys results in the phase transformation from the paramagnetic, chemically ordered B2-phase to the ferromagnetic, chemically disordered A2-phase. The magnetic phase transformation is related to the number of displacements per atom (dpa) during the irradiation. For heavy ions (Ar⁺, Kr⁺, Xe⁺) a universal curve is observed with a steep increase in the fraction of ferromagnetic phase reaching saturation, i. e., a complete phase transformation, at about 0.5 dpa. This proves the purely ballistic nature of the disordering process. If light ions are used (He⁺, Ne⁺) a pronounced deviation from the universal curve is observed. This is attributed to bulk vacancy diffusion from dilute collision cascades, which leads to a partial recovery of the thermodynamically favored B2-phase. Comparing different noble gas ion irradiation experiments allows to asses the corresponding counteracting contributions. In addition, the potential to create local ferromagnetic areas embedded in a paramagnetic matrix is demonstrated.