Berlin 2005 – scientific programme
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MA: Magnetismus
MA 20: Poster:Schichten(1-29),Spintrsp(30-45),Ex-Bias(46-63),Spindyn(64-75),Mikromat.(76-80),Cluster(81-94),Abbv.(95-99),Obflm(100-02),SpElek.(103-09),E-Theo(110-14),Mikromag.(115-16),Spin+PÜ(117-26),Mag.Mat.(127-51),Meth.(152-55),Mol.Mag(156-59),Kondo(160-65
MA 20.59: Poster
Monday, March 7, 2005, 14:00–18:00, Poster TU C
Asymmetric fixed and rotatable magnetic anisotropy at the onset of exchange bias — •Jeffrey McCord1 and Roland Mattheis2 — 1Leibniz Institute for Solid State and Materials Research Dresden - Institute for Metallic Materials - 01169 Dresden — 2Institut für physikalische Hochtechnologie IPHT Jena - 07745 Jena
The strength of exchange bias and rotatable anisotropy in polycrystalline NiFe/IrMn ferromagnet/antiferromagnet systems is quantified from dc down to the ps time-scale by regular quasi-static and microwave magnetometry, as well as magnetic domain observation. A transition from superparamagnetic to antiferromagnetic behavior with increasing IrMn thickness is derived from the magnetic resonance frequency and the effective magnetic damping parameter. A discrepancy between magnetic loop shift and dynamically obtained exchange bias strength is explained by asymmetric rotatable anisotropy contributions with different relaxation times in the antiferromagnetic layer. The time dependent relaxation is directly confirmed by magnetic domain observations. Partially switching in the IrMn layer even with strong exchange bias is concluded. The increase of coercivity rises solely from the rotatable anisotropy contribution.