Growth, structural and magnetic properties of high coercivity Co/Pt multilayers

Journal Article · Wed Nov 01 04:00:00 EST 2000 · Journal of Applied Physics

OSTI ID:787092

Weller, D ^[1]; Folks, L; Best, M; Kusinski, G J; Krishnan, K M; Thomas, G

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1. LBNL Library

Co/Pt multilayer films ([Co (tCo nm)/Pt(1 nm)]10, 0.2 < tCo < 2 nm) with perpendicular magnetic anisotropy and room temperature coercivity Hc = 12-15 kOe are fabricated using electron beam evaporation at elevated growth temperatures onto Si(001)/SiNx(40nm)/Pt(20nm) substrate/seed structures. Hysteresis and magnetic force microscopy (MFM) studies indicate changes in the magnetization reversal mechanism along with a sharp increase in coercivity for growth temperatures higher TG {approx} 230 - 250 degrees C. Films grown at TG < 230 degrees C (tCo = 0.2 - 0.4 nm) show large micrometer size magnetic domains and rectangular hysteresis loops indicating magnetization reversal dominated by rapid domain wall motion throughout the film following nucleation at Hn {approx} Hc. Films grown at TG > 250 degrees C show fine-grained MFM features on the sub-100 nm length scale and hysteresis studies indicate reversal dominated by localized switching of small clusters. The hysteresis curves for the highest coercivity films are sheared with a hysteresis slope alpha=4(pi)dM/dH|Hc approximately equal 1.5, which is close to the ideal value for completely decoupled grains of alpha =1. High resolution cross-sectional TEM with elemental analysis shows columnar grains extending throughout the multilayer stack. Sharp Co/Pt interfaces are found from TEM and grazing incidence X-ray diffraction. At higher TG, Co depletion and structural defects at the grain boundaries provide a mechanism for exchange decoupling of adjacent grains, which may result in the high coercivities observed. Anisotropy and magnetization values are estimated as Ku {approx} 8x106 erg/cc and MS {approx} 450 emu/cc (per total volume), hence Hk = 2Ku/MS {approx} 17.5 kOe for the highest coercivity Hc {approx} 15 kOe films.

• Research Organization: Lawrence Berkeley National Lab., CA (US)
• Sponsoring Organization: USDOE Director, Office of Science. Office of Basic Energy Studies. Division of Materials Sciences (US)
• DOE Contract Number: AC03-76SF00098
• OSTI ID: 787092
• Report Number(s): LBNL--46718
• Journal Information: Journal of Applied Physics, Journal Name: Journal of Applied Physics Journal Issue: 11 PT2 Vol. 89; ISSN JAPIAU; ISSN 0021-8979
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
CO/PT MAGNETIC MULTILAYERS STRUCTURE HIGH COERCIVITY
COBALT
CRYSTAL DEFECTS
CRYSTAL GROWTH
ELECTRON BEAMS
ENERGY BEAM DEPOSITION
GRAIN BOUNDARIES
MAGNETIC PROPERTIES
PLATINUM
SILICON
SILICON NITRIDES