| Autor: |
Chi, J. H., Ge, S. H., Liu, C. M., Kunkel, H. P., Zhou, X. Z., Williams, G. |
| Předmět: |
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| Zdroj: |
Journal of Applied Physics; 5/15/2003, Vol. 93 Issue 10, p6188, 4p, 1 Black and White Photograph, 7 Graphs |
| Abstrakt: |
Co - MgF[SUB2] granular films were deposited on glass substrates by rf co-sputtering at room temperature (RT). The influence of the Co volume fraction, f[SUBv], of these granular films on the tunneling magnetoresistance (TMR) and magnetic properties was studied systematically. In a magnetic field of 1.2 T, the TMR value at RT initially increases gradually with decreasing f[SUBv], reaches its maximum value of -8% for f[SUBv]=0.38, and then decreases. The corresponding magnetization curves indicate a change from ferromagnetism to superparamagnetism. A minimum in the coercivity, H[SUBc],(11 Oe) is obtained in the Co[SUB50]MgF[SUB2])[SUB50] granular film which also has a large zero field resistivity. This) magnetically soft granular film may consequently be a good candidate for high frequency applications. These variations of the TMR and magnetic properties can be ascribed to gradual changes in the film microstructure with decreasing f[SUBv], from interconnected metallic Co grains to nano-scaled Co particles dispersed in a crystallized insulating MgF[SUB2] matrix. The zero field cooled (ZFC) and field cooled (FC) curves for the samples were obtained in the temperature range 5-300 K in various magnetic fields. The peak in the ZFC curve shifts gradually towards lower temperature with increasing applied magnetic field and, with increasing f[SUBv], the peak temperature decreases more quickly with increasing field. The latter indicates that the magnetic interactions between grains become stronger, consistent with model predictions. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
| Externí odkaz: |
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