We report on the study of high frequency magnetotransport properties of the chromium dioxide (CrO 2) thin films, grown on Si substrate using chemical vapor deposition. The film exhibits a ferromagnetic transition with a Curie temperature near 390 K. The temperature dependent spontaneous magnetization follows Bloch's law. The impedance spectra, being analyzed based on the fundamental electrodynamics, are demonstrated to be in a low-loss dielectric limit along with the occurrence of dielectric relaxation and magnetization response. The specific features of impedance spectra, distinct from the usual metallic ferromagnet, are attributed to the half metallic nature of CrO 2. The results explore the possibility for high frequency device applications.
The impedance of chemical vapor deposited CrO 2 and Cr 2 O 3 bilayered thin films, composed of polycrystalline and amorphous structure, have been systematically studied in function of frequency and temperature. In the polycrystalline-CrO 2 /amorphous-Cr 2 O 3 bilayer, the real part of impedance at low frequency ( f Ͻ300 kHz) demonstrates a sharp transition at temperature around 330 K, with a specific feature of positive temperature coefficient, similar to the variation of dc resistance occurs at ferroelectric-paraelectric transition in the BaTiO 3 ceramics. In contrast, the imaginary part of impedance, at frequency f Ͼ300 kHz, shows a characteristic of negative temperature coefficient. Further analysis of the frequency dependence of the impedance shows the contribution from the dynamics of both the dielectric and magnetic dipoles in the layers. Comparison of polycrystalline-CrO 2 and amorphous-Cr 2 O 3 single layer with the CrO 2 /Cr 2 O 3 bilayer is discussed.
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