Structure and Magnetic Switching of Thin Film HITPERM/SiO2 Soft Magnetic Multilayers

Published

July 4, 2004

Author(s)

Hideyuki Okumura, C Y. Um, S Y. Chu, M E. McHenry, D E. Laughlin, Anthony B. Kos

Abstract

Laminated (Fe_0.7Co_0.3)₈₈Zr₇B ₄Cu a-HITPERM/SiO₂ multilayer thin films have been previously shown to exhibit thermally activated, stepped magnetization curves associated with sequential switching of layers. A model for the thickness dependence of the coercivity and its reduction in multilayers is reviewed along with new measurements of room temperature pulsed inductive microwave magnetometry (PIMM) in single, bi- and tri-layer films. We detail switching in a multilayer film with six (50 nm thick) HITPERM layers, separated by five(2 nm thick) SiO₂ layers designed to increase the total moment of the films. Films were investigated using conventional TEM and high resolution TEM (HREM), and SQUID magnetometry. HREM and TEM studies reveal BCC FeCo nanocrystals to nucleate on top of SiO₂ layers with the top layer having a larger volume fraction of coarser nanocrystallites. The crystallites have larger magnetization than amorphous regions. Plan view TEM on the top layer reveals FCC nanocrystals to align in chains with spacing of approximately equal}50-100 nm. SQUID magnetometry shows that after saturation, reversal begins by a rotation mechanism in a single layer for (H less than or equal to} 180 Oe) followed by the nearly simultaneous reversal of several layers. The final switching event is thermally activated requiring fields in excess of 100 Oe to switch at 2 K, but switching at the same field as other layers for elevated temperatures (RT).

Citation

IEEE Transactions on Magnetics

Volume

40

Pub Type

Journals

Keywords

HITPERM, multilayer thin films, nanocrystallites, pulsed inductive microwave magnetometer, TEM

Citation

Okumura, H. , Um, C. , Chu, S. , McHenry, M. , Laughlin, D. and Kos, A. (2004), Structure and Magnetic Switching of Thin Film HITPERM/SiO₂ Soft Magnetic Multilayers, IEEE Transactions on Magnetics (Accessed December 7, 2024)