Spin-glass-like freezing of inner and outer surface layers in hollow {\gamma}Fe$_2$O$_3$ nanoparticles

  title={Spin-glass-like freezing of inner and outer surface layers in hollow \{\gamma\}Fe\$\_2\$O\$\_3\$ nanoparticles},
  author={Hafsa Khurshid and Paula Lampen-Kelley and {\`O}scar Iglesias and Javier Alonso and Manh Huong Phan and Cheng-Jun Sun and Marie-Louise Saboungi and Hariharan Srikanth},
  journal={arXiv: Materials Science},
Disorder among surface spins largely dominates the magnetic response of ultrafine magnetic particle systems. In this work, we examine time-dependent magnetization in high-quality, monodisperse hollow maghemite nanoparticles with a 14.8 $\pm$ 0.5 nm outer diameter and enhanced surface-to-volume ratio. The nanoparticle ensemble exhibits spin-glass-like signatures in dc magnetic aging and memory protocols and ac magnetic susceptibility. The dynamics of the system slows near 50 K, and becomes… 

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