Magnetic and Electronic Properties of Point Defects in ZrO2

Using the Korringa–Kohn–Rostoker Coherent Potential Approximation (KKR-CPA) method in connection with the Generalized Gradient Approximation (GGA), we study the magnetic and electronic properties of different point defects in cubic ZrO₂. In particular, we discuss the zirconium interstitial (Zr_i), zirconium antisite (Zr_O), zirconium vacancy (V_Zr), oxygen interstitial (O_i), oxygen antisite (O_Zr), and oxygen vacancy (V_O) defects. It has been shown that oxygen vacancy and zirconium interstitial (V_O, Zr_i) are n-type, while the other point defects are p-type. The magnetic moments are observed only in the oxygen interstitial and antisite (O_i, O_Zr) cases. The corresponding ferromagnetic states are more stable than the spin–glass states. It has been found that the mechanism responsible of such stabilities is the double exchange. Based on Mean Field Approximation (MFA), the Curie temperature (T _C ) is estimated. Moreover, it has been found that the O_i and O_Zr defects provide half-metallic properties being the responsible for ferromagnetism.     

Wetting and Layering Transitions in a Nano-Square Structure: Monte Carlo Study

In this work, we study the magnetic wetting and layering transitions in a nano-square structure. The system is consisting of particles with spins s= 1/2 and S=1 placed at the square sites. We study the effect of the exchange couplings between different spins, namely, s- s, S- s, and S-S. The wetting phenomena and layering transitions are found under the effect of the temperature and the external magnetic field, for fixed values of the exchange coupling parameters. When studying the temperature effect on the magnetizations, using Monte Carlo simulations, the ground-state phase diagrams confirm these results for very low temperatures. Over the 2 × 2 × 2 × 3 = 24 possible configurations, only 6 configurations are found to be stable in the ground-state phase diagrams. Though the model established equations are valid for any system sizes, we give results and numerical values for a fixed system size formed only by four square layers.     

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Journal of Materials Science: Materials in Electronics -