| AVS 65th International Symposium & Exhibition | |
| Spectroscopic Ellipsometry Focus Topic | Monday Sessions |
| Session EL+EM-MoA |
| Session: | Spectroscopic Ellipsometry: Novel Applications and Theoretical Approaches |
| Presenter: | Farzin Abadizaman, New Mexico State University |
| Authors: | F. Abadizaman, New Mexico State University S. Zollner, New Mexico State University |
| Correspondent: | Click to Email |
Magnetized Ni demonstrates an anomaly in its optical constants near the Curie temperature (Tc = 627 K). Experiment shows that this anomaly does not depend on the morphology of the sample. To investigate this feature, we have carried out a series of ellipsometry measurements in the energy range of 0.5 to 6.5 eV as a function of temperature from 80 to 800 K in 25 K steps. Furthermore, temperature dependent Mueller Matrix (MM) measurements have been performed on the magnetized Ni at a single energy of 1.97 eV as a series of four runs, up and down, between 300 and 800 K. The MM data of magnetized Ni reveal slight changes in the anisotropic portion of the MM while passing Tc. However, vast changes in the isotropic MM elements are found, indicating that the anomaly is not due to the induced anisotropy of the sample. The anomaly occurs only in the first run when the temperature passes Tc, which suggests that it stems from magnetization. On the other hand, magnetizing the sample again and repeating the experiment do not demonstrate any anomaly as passing Tc, which disproves our previous suggestion. In fact, the anomaly happens only once for each sample, regardless of its morphology.
No observable variation in the out-of-plane grain sizes were found in the XRD data before and after the temperature measurement. This and the fact that the anomaly occurs for a single crystalline sample as well as for a polycrystalline one indicate that it cannot be due to the grain growth. This turned our attention to the surface effects: Several experiments have been conducted to investigatehow the surface of sample changes around Tc and how cleaning the surface affects the optical constants of Ni. The authors believe that the anomaly around Tc originates from the surface changes. Yet the question of why it occurs near Tc is still open. The same series of experiments have been performed on cobalt and the results are compared to Ni.