One-Pot Synthesis and Characterization of Size-Controlled Bimagnetic FePt-Iron Oxide Heterodimer Nanocrystals

A one-pot, two-step colloidal strategy to prepare bimagnetic hybrid nanocrystals (HNCs),
comprising size-tuned fcc FePt and inverse spinel cubic iron oxide domains epitaxially arranged in a
heterodimer configuration, is described. The HNCs have been synthesized in a unique surfactant
environment by temperature-driven sequential reactions, involving the homogeneous nucleation of FePt
seeds and the subsequent heterogeneous growth of iron oxide. This self-regulated mechanism offers high
versatility in the control of the geometric features of the resulting heterostructures, circumventing the use
of more elaborate seeded growth techniques. It has been found that, as a consequence of the exchange
coupling between the two materials, the HNCs exhibit tunable single-phase-like magnetic behavior, distinct
from that of their individual components. In addition, the potential of the heterodimers as effective contrast
agents for magnetic resonance imaging techniques has been examined.