Dupré, Luc

Olyslager, Femke

Van de Wiele, Ben

Undetermined

Ghent University Academic Bibliography

HYSTERESIS MODELING AND MICROMAGNETICS 2007 - NAPLES JUNE 4-6 2007, ITALY 101Memory properties in a 3D micromagneticmodel for ferromagnetic samplesB. Van de Wiele, L. Dupre´, F. OlyslagerI. IntroductionHysteresis modelling describes the transitioncurves corresponding with any change of the mag-netic applied field. General features in the magne-tization process are observed, known as Madelung’srules. Two major properties are the return-point-memory and the wiping-out-property [1]. Scalarmacroscopic magnetic hysteresis models incorporatethese rules. Here we show that the three dimen-sional micromagnetic model for large, bulk like sam-ples presented in [2] incorporates Madelung’s rules.II. Numerical verification in themicromagnetic modelTo evaluate the magnetic memory behavior, aniron sample with dimensions of 0.48µm×0.96µm×0.48µm consisting of two grains is simulated. Micro-scopic stresses are added to simulate grain boundarystresses. The sample is divided in cubical finite dif-ference (FD) cells of 7.5nm. In each cell, a magneticdipole is defined. The evolution of the applied fieldis shown in Fig. 1. In Fig. 2, the magnetization0 5 10 15−505x 105a b c d e ft [s]H a [A/m]Fig. 1. Evolution of the applied field along the longest edgeof the samplestates in a plane parallel with the applied field attime points c and e are shown. The states are iden-tical. This is also shown in Table I where the differ-ences between the magnetization states depicted inFig. 1 are shown. Here, the difference ∆(A ↔ B)between two magnetic states A and B is defined asB. Van de Wiele and L. Dupre´ are with the Department ofElectrical Energy, Systems and Automation, F. Olyslager iswith the Department of Information Technology, both GhentUniversity, Sint-Pietersnieuwstraat 41, B-9000 Ghent, Bel-gium. E-mail: ben.vandewiele@ugent.bethe mean angle (in degrees) between the magneticdipoles in corresponding FD cells of state A and B.Fig. 2. Magnetic states in a plane parallel with the appliedfield, in time points c (top) and e (bottom), cfr Fig. 1TABLE Idifference in magnetization state [degrees]∆(a↔ f) 4.33 ∆(c↔ e) 2.94∆(a↔ b) 77.73 ∆(c↔ d) 20.22III. ConclusionsSince the differences ∆(a↔ f) and ∆(c↔ e) aresmaller then computational errors [2] while the otherstates b and d differ substantially one concludes that(1) minor hysteretic loops are closed (return-point-memory) (2) the closed minor loops are completelyerased from the memory (wiping-out-property) and(3) the magnetic state at the start of a minor loopis recovered exactly when this loop is closed.References[1] E. Madelung, Annalen der Physik, vol.17, 1905, pp 861-890.[2] B. Van de Wiele, F. Olyslager and L. Dupre´, ”Fast nu-merical 3D-scheme for the simulation of hysteresis in fer-romagnetic grains”, accepted for publication in Journalof Applied Physics.56

Memory properties in a 3D micromagnetic model for ferromagnetic samples (abstract)

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Memory properties in a 3D micromagnetic model for ferromagnetic samples (abstract)

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