Low-field magnetization study of CoFe-A1(2)O(3) multilayers

• Type: Article in International Scientific Journal
• Date: 2003

Authors

G.N. Kakazei (Author) Other; pogorelov, y. g. (Author) FCUP; Santos, JAM (Author) Other; sousa, j. b. (Author) FCUP; Freitas, PP (Author) Other; Cardoso, S (Author) Other; Lesnik, NA (Author) Other; Wigen, PE (Author) Other

Journal

Title: Journal of Magnetism and Magnetic Materials

Vol. 266

Pages: 57-61

ISSN: 0304-8853

Publisher: Elsevier

Indexing

ISI Web of Knowledge - 15 Citations

Scopus - 15 Citations

Other information

Authenticus ID: P-000-F0J

DOI: 10.1016/s0304-8853(03)00455-4

Abstract (EN): Zero-field-cooled (ZFC) and field-cooled (FC) magnetization curves were recorded for a series of ion-beam-deposited metal-insulator CoFe(t)/Al2O3(30Angstrom) multilayers, ranging from discontinuous insulating (t = 9Angstrom) to continuous metallic (t = 25Angstrom) behavior, for temperatures T from 8 to 300 K and in applied magnetic fields H from 10 to 100 Oe. Data allow the analysis of the different magnetic phases coexisting in this system. The superferromagnetic (SFM) fraction is characterized by the Curie temperature, T-C, and ZFC remanence at T --> 0, M-SFM, both being functions of the CoFe nominal thickness t. The remaining superparamagnetic (SPM) fraction starts getting blocked below a certain blocking temperature T-b, which depends both on t and H. The SFM phase develops above some critical thickness t(cr) approximate to 11Angstrom, so that M-SFM(t) is almost linear: M-SFM proportional to (t - t(cr)), at t(cr) < t < t(p), and attains the maximum (bulk) value at t --> t(p) approximate to 18Angstrom, which is the metallic percolation threshold. In the SFM-SPM coexistence range t(cr) < t < t(p), the blocking temperature Tb shows a monotonic increase with thickness t but a pronounced decrease with field H. This latter effect is attributed to field-induced suppression of the energy barriers for alignment of pre-formed domains in the SFM fraction.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 5