Morphology and Magnetic Properties of PtCo Nanoparticles

MIZRAHI M.; GIOVANETTI, L, J.; J.M. RAMALLO LÓPEZ; G. KRYLOVA; E. V. SHEVCHENKO; F. G. REQUEJO

Cancun

Congreso; XXII International Materials Research Congress; 2013

Materials Research Society

Multicomponent nanocrystals (MNCs) became an important class of materials due to their abilities to carry multiple functions that can be utilized simultaneously [1]. Recent progress in synthesis of MNCs allowed obtaining different types of nanoparticles (NPs) such as core-shells [2], dumbbells, or other geometries [3]. Synthesis of such structures is often based in the nucleation of the second component on the seed material. In this work we present the study of bimetallic CoPt nanoparticles. The characterization was performed using transmission electron microscopy (TEM), X-ray absorption (XAS), X-ray scattering at low angle (SAXS), global magnetic measurements (MM) and magnetic circular dichroism measurements (XMCD). Combination of TEM and SAXS results show spherical particles with a size dispersion of about 5% for PtCo system. Combination of EXAFS results at the Pt L3 edge and Co K edge reveals a core-shell structure formation. From MM it is observed that all samples exhibit superparamagnetic behavior at RT with a blocking temperature (TB) that decreases for smaller PtCo MNCs. XMCD at the Pt-L3 edge measurements show that there is a transfer of magnetic moment from Co to Pt atoms. The variation of the XMCD intensity signal with temperature is in accordance with changes in the global MM. This shows that the Co atoms, through alloy formation with the Pt atoms, is the main responsible for the appearance of the XMCD signal at the Pt L3 edge.