Interparticle magnetic correlations in dense Co nanoparticle assemblies

Resonant magnetic x-ray scattering from dense self-assemblies of 9-nm diameter epsilon-Co and hcp-Co particles is reported. For lower anisotropy epsilon-Co we find remanent magnetic scattering that is significantly enhanced, indicating preferred inter-particle moment orientations of both antiferromagnetic and ferromagnetic character. This interaction-mediated collective behavior is consistent with dipolar fields and exists well above the isolated particles blocking temperature where thermal activation is operative, suggesting that magnetostatic super-spin waves exist in such systems.

报道了来自直径为9纳米的ε - Co和hcp - Co颗粒的密集自组装体的共振磁X射线散射。对于各向异性较低的ε - Co，我们发现剩余磁散射显著增强，这表明存在反铁磁和铁磁特性的颗粒间择优磁矩取向。这种由相互作用介导的集体行为与偶极场一致，并且在热激活起作用的孤立颗粒阻塞温度之上仍然存在，这表明在这类系统中存在静磁超自旋波。