The effect of magnetic anisotropy-axis alignment of individual nanoparticles on the collective aging behavior in the superspin glass state of a frozen ferrofluid has been investigated. The ferrofluid studied here consists of maghemite nanoparticles (\gamma-Fe2O3, mean diameter = 8.6 nm) dispersed in glycerin at a volume fraction of ~15%. The low temperature aging behavior has been explored through 'zero-field cooled magnetization' (ZFCM) relaxation measurements using SQUID magnetometry. The ZFCM response functions were found to scale with effective age of the system in both textured and non-textured superspin glass states, but with markedly different scaling exponents, \mu. The value of {\mu} was found to shift from ~0.9 in non-textured case to ~ 0.6 in the textured case, despite the identical cooling protocol used in both experiments.
@article{arxiv.1009.2609,
title = {Superspin glass aging behavior in textured and nontextured frozen ferrofluid},
author = {Sawako Nakamae and Emmanuelle Dubois and Vincent Dupuis and Denis L'Hôte and Régine Perzynski and Eric Vincent and Caroline Thibierge},
journal= {arXiv preprint arXiv:1009.2609},
year = {2010}
}