Magnetism of monomer MnO and heterodimer FePt@MnO nanoparticles

Article

关键词: POLARIZATION ANALYSIS;    EXCHANGE-ANISOTROPY;   

DOI  :  10.1103/PhysRevB.95.134427

来源: SCIE

【 摘 要 】

We report about the magnetic properties of antiferromagnetic (AF) MnO nanoparticles (NPs) with different sizes (6-19 nm). Using a combination of polarized neutron scattering and magnetometry, we were able to resolve previously observed peculiarities. Magnetometry, on the one hand, reveals a peak in the zero-field-cooled (ZFC) magnetization curves at low temperatures (similar to 25 K) but no feature around the N'eel temperature at 118 K. On the other hand, polarized neutron scattering shows the expected behavior of the AF order parameter vanishing around 118 K. Moreover, hysteresis curves measured at various temperatures reveal an exchange-bias effect, indicating a coupling of an AF core to a ferromagnetic (FM)-like shell. ZFC data measured at various fields exclude a purely superparamagnetic (SPM) scenario. We conclude that the magnetic behavior of MnO particles can be explained by a superposition of SPM-like thermal fluctuations of the AF-N ' eel vector inside the AF core and a magnetic coupling to a ferrimagnetic Mn2O3 or Mn3O4 shell. In addition, we have studied heterodimer (Janus) particles, where a FM FePt particle is attached to the AFMnO particle. Via the exchange-bias effect, the magnetic moment of the FePt subunit is stabilized by the MnO.

【 授权许可】

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