Morphology and Magnetic Properties of PtCo Nanoparticles

MARTÍN DANIEL MIZRAHI; LISANDRO J. GIOVANETTI; JOSE MARTIN RAMALLO LOPEZ; KRYLOVA, G.; E.V. SHEVCHENKO; F. G. REQUEJO

Cancún

Congreso; XXII International Materials Research Congress (IMRC) 2013; 2013

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 Co-Pt nanoparticles. The characterization was performed using 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 that decreases in smaller PtCo MNCs. XMCD at the Pt-L3 edge measurements show that there is a transfer of magnetic moment from Co atoms to Pt. The variation of the XMCD intensity signal with temperature is in accordance with changes in the magnetization of the PtCo alloy. This shows that the Co atoms, through the formation of alloy with the Pt, is the main responsible for the appearance of the XMCD signal, but cannot rule out a contribution from the size of NPs.