| Autor: |
Sergeenkov, S., Souza, N. S., Speglich, C., Rivera, V. A. G., Cardoso, C. A., Pardo, H., Mombru, A. W., Araujo-Moreira, F. M. |
| Rok vydání: |
2009 |
| Předmět: |
|
| Zdroj: |
Journal of Applied Physics 106, 116101 (2009) |
| Druh dokumentu: |
Working Paper |
| DOI: |
10.1063/1.3264571 |
| Popis: |
In addition to the double phase transition (with the Curie temperatures T_C=300K and T_{Ct}=144K), a low-temperature anomaly in the dependence of the magnetization is observed in the bulk magnetic graphite (with an average granular size of L=10nm), which is attributed to manifestation of the size effects below the quantum temperature. The best fits of the high-temperature data (using the mean-field Curie-Weiss and Bloch expressions) produced reasonable estimates for the model parameters, such as defects mediated effective spin exchange energy J=12meV (which defines the intragranular Curie temperature T_C) and proximity mediated interactions between neighboring grains (through potential barriers created by thin layers of non-magnetic graphite) with energy J_t=exp(-d/s)J=5.8meV (which defines the intergranular Curie temperature T_{Ct}) with d=1.5nm and s=2nm being the intergranular distance and characteristic length, respectively. |
| Databáze: |
arXiv |
| Externí odkaz: |
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