Dresden 2017 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 26: Thin Films: Magnetic Coupling Phenomena / Exchange Bias
MA 26.8: Vortrag
Dienstag, 21. März 2017, 15:45–16:00, HSZ 101
ns-laser driven magnetic phase transition in FeAl — •Maciej Oskar Liedke1, Rantej Bali2, Elzbieta Gradauskaite1, Jonathan Ehrler2, Mao Wang2, Kay Potzger2, Shengqiang Zhou2, and Andreas Wagner1 — 1Institute of Radiation Physics, HZDR, Dresden, Germany — 2Institute of Ion Beam Physics and Materials Research, HZDR, Dresden, Germany
FeAl alloys show temperature dependent magnetic phase transition (MPT) from a ferromagnetic disordered A2-phase to a paramagnetic ordered B2-phase. The B2-phase can be reversed back to the A2-phase, e.g, by ion irradiation. The most plausible explanation of MPT points in direction of the anti-site disorder (ASD), i.e., more Fe-Fe nearest neighbors due to disordering. However, variations of the lattice parameter, defects concentration, and secondary phases may play an important role, too. Here, we employ an excimer UV ns-laser to examine the role of ASD and defects onto magnetic properties. Three sample series with different initial order conditions were irradiated by several laser fluences: (i) as-grown semi-, (ii) Ne irradiated fully-disordered, and (iii) vacuum annealed ordered alloys. Two magnetic regimes were found depending on laser fluence: (i) in the low fluence range magnetization initially decreases, followed by (ii) subsequent monotonic increase for larger fluences. The positron annihilation spectroscopy measurements reveal changes of defects surrounding from Al- to Fe-dominant, respectively, as well as of defects concentration. The results obtained by MOKE, VSM, AFM, and TEM will be discussed in detail.