2007
DOI: 10.1063/1.2736303
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Observation of Co/CoO nanoparticles below the critical size for exchange bias

Abstract: We compare the magnetic properties of pure and oxidized Co nanoparticles embedded in an amorphous Al 2 O 3 matrix. Nanoparticles with diameters of 2 or 3 nm were prepared by alternate pulsed laser deposition in high vacuum conditions, and some of them were exposed to O 2 after production and before being embedded. The nanoparticles are organized in layers, the effective edge-to-edge in-depth separation being 5 or 10 nm. The lower saturation magnetizations per Co atom for the samples containing oxidized nanopar… Show more

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Cited by 32 publications
(19 citation statements)
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“…Pure LSMO is a soft magnet with coercivity field H CLSMO ≈ 5 Oe and pure SFO is a hard ferrimagnet with coercivity field H CSFO ≈ 1.12 kOe. However, for the composite, it exhibits a clear enhanced coercive field (Table 1), which implies the existence of antiferromagnetic (AFM) coupling between LSMO and SFO grains [28]. In addition, the magnetization of the composite (1 − x)LSMO:xSFO is lower than the sum of experimental magnetization of LSMO and SFO (Table 1), this reduced magnetization also demonstrates that enhanced magnetic disorder and AFM coupling exists between LSMO and SFO grains [29].…”
Section: Resultsmentioning
confidence: 85%
“…Pure LSMO is a soft magnet with coercivity field H CLSMO ≈ 5 Oe and pure SFO is a hard ferrimagnet with coercivity field H CSFO ≈ 1.12 kOe. However, for the composite, it exhibits a clear enhanced coercive field (Table 1), which implies the existence of antiferromagnetic (AFM) coupling between LSMO and SFO grains [28]. In addition, the magnetization of the composite (1 − x)LSMO:xSFO is lower than the sum of experimental magnetization of LSMO and SFO (Table 1), this reduced magnetization also demonstrates that enhanced magnetic disorder and AFM coupling exists between LSMO and SFO grains [29].…”
Section: Resultsmentioning
confidence: 85%
“…For instance, the anisotropy energy of a CoO shell is proportional to the term (R 3 − r 3 ), where R and r are the particle and the core radius, respectively. 35 Accordingly, the intensity of exchange interaction may increase significantly as shell thickness grows, keeping the core radius constant, till anisotropy energy overcomes the effective Zeeman energy of the FM core. In this case anisotropy energy is expected to be double for sample 4, explaining the rise of exchange bias.…”
Section: Magnetic Characterizationmentioning
confidence: 99%
“…The composite exhibits a clear magnetic hysteresis loop with corresponding coercive field 360 Oe, larger than that of pure CuFe 2 O 4 (280 Oe) measured at 1 T, contrast to that observed in LSMO/BaFe 11.3 (ZnSn) 0.7 O 19 composite [12] where the coercive field is softened. This enhanced coercivity of the composites implies the existence of antiferromagnetic (AFM) coupling between LCMO and CuFe 2 O 4 grains, which usually observed in FM-AFM systems [18,19]. For this case, the existence of LCMO can obstruct the ferromagnetic coupling between CuFe 2 O 4 grains and exert an additional magnetic torque during magnetization rotation of CuFe 2 O 4 grains, which make the CuFe 2 O 4 FM spins rotation difficult, as a result, the increase of coercive field is observed in composites.…”
Section: Resultsmentioning
confidence: 98%