Regensburg 2000 – wissenschaftliches Programm
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AM: Magnetismus
AM 7: Dauermagnete, nanokristalline hart- und weichmagnetische Werkstoffe
AM 7.8: Vortrag
Montag, 27. März 2000, 17:15–17:30, H10
Evolution of the magnetic configuration of Sm-Co/Fe bilayers in an applied magnetic field — •W. Donner1, B. Nickel1, G.P. Felcher2, and J.S. Jiang2 — 1MPI für Metallforschung, 70569 Stuttgart, Germany — 2Argonne National Laboratory, Materials Science Division, Argonne IL 60439, USA
Exchange spring magnets are systems with novel magnetic properties obtained by coupling a layer of material with high coercivity with a layer of material of high magnetization. One of the most studied systems is obtained by sputtering epitaxially a layer of Sm-Co onto a (110) face of MgO, and capping it with an iron layer. For layers with a thickness of a few hundred Å the magnetization of Sm-Co is rigidly directed along the (001) direction of the substrate MgO. An exchange-spring magnet is obtained by covering Sm-Co with a layer of Fe of similar thickness. The magnetic response of the bilayer to a magnetic field away from the easy axis is interpreted in terms of a micromagnetic model, where the moments of the Fe planes close to the surface align with the field, while those close to the Sm-Co interface remain aligned along the easy axis. Polarized neutron reflectivity confirmed the existence of a magnetic "spring" in iron, but also evidenced an unexpected reorientation of the moments of Sm-Co, with a sizeable component perpendicular to the plane of the film. The effect is to be related to the coarse, needle like growth of sputtered Sm-Co, and is probably responsible for the drastic decrease of the coercive field of Sm-Co when covered with iron.
Work at ANL supported by USDOE, Office of Science, under contract W-31-109-ENG-38.