Low temperature spin-glass-like phases in magnetic nano-granular composites
KAUST DepartmentImaging and Characterization Core Lab
Physical Sciences and Engineering (PSE) Division
Advanced Nanofabrication, Imaging and Characterization Core Lab
Materials Science and Engineering Program
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AbstractIt is a common understanding that the dipole-dipole interaction among the magnetic nanoparticles may result in a low-temperature spin-glass phase, which has been evidenced by observation of aging effect and memory effect. However, several studies on the nano-particles systems showed that some of the observed spin-glass-like phenomena could be due to the existence of spin-glasslike shells surrounding the ferrimagnetic cores. Therefore, it is very important to understand that how the dipole-dipole interaction induce the spin-glass phase. In order to address this issue, we have fabricated Co-SiO 2 and Fe-SiO 2 nano-granular thin films and measured the memory effect for them. Spin-glass-like phase has been observed at low temperatures. We found that, after annealing, the size of the clusters increased significantly. Based on a simple model, the dipole-dipole interaction between the clusters must be increased accordingly for the annealed samples. Interestingly, the memory effect is greatly weakened in the annealed films, which strongly suggested that the dipole-dipole interaction may not be the major factor for the formation of the low-temperature spin-glass-like phase. Copyright © 2012 American Scientific Publishers All rights reserved.
PublisherAmerican Scientific Publishers