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Evidence of random magnetic anisotropy in ferrihydrite nanoparticles based on analysis of statistical distributions

2008; American Physical Society; Volume: 77; Issue: 13 Linguagem: Inglês

10.1103/physrevb.77.134426

1550-235X

Nuno J. O. Silva, V. S. Amaral, Luís D. Carlos, Benito Rodríguez‐González, Luis M. Liz‐Marzán, Thelma S. Berquó, Subir K. Banerjee, V. de Zea Bermudez, Ángel Millán, F. Palacio,

Magnetic properties of thin films

We show that the magnetic anisotropy energy of antiferromagnetic ferrihydrite depends on the square root of the nanoparticles' volume, using a method based on the analysis of statistical distributions. The size distribution was obtained by transmission electron microscopy, and the anisotropy energy distributions were obtained from ac magnetic susceptibility and magnetic relaxation. The square root dependence corresponds to random local anisotropy, whose average is given by its variance, and can be understood in terms of the recently proposed single phase homogeneous structure of ferrihydrite.