A quantum-mechanical method for estimating the cation distribution in spinel ferrites is proposed, by which the ionization energy of the cations and the Pauli repulsion energy is considered, together with the magnetic ordered energy and the tendency toward charge density balance. Using this method, not only can the difference between the observed and the traditional theoretical magnetic moments of the spinel structure ferrites MFe2O4 (M=Mn,Fe,Co,Ni,Cu) be explained, but also the dependence of the magnetic moments of the ferrites M1−xZnxFe2O4 (M=Mn,Fe,Co,Ni,Cu) on the doping level x can be fitted.
Doped HfO2 has become a promising candidate for non-volatile memory devices since it can be easily integrated into existing CMOS technology. Many dopants like Y, Gd, and Sr have been investigated for the stabilization of ferroelectric HfO2. Here, we report the fabrication of capacitors comprising ferroelectric HfO2 metal-insulator-metal structures with TiN bottom and top electrodes using the dopant Lu. Amorphous 5% Lu doped HfO2 was deposited by pulsed laser deposition and afterwards annealed to achieve the ferroelectric, orthorhombic phase (space group Pbc21). The polarization of the layers was confirmed by capacitance-voltage, polarization-voltage, and current-voltage measurements. Depending on the anneal temperature, the remanent polarization changes and the initial state of the oxide varies. The layer exhibits initially a pinched hysteresis up to an annealing temperature of 600 °C and an unpinched hysteresis at 700 °C. The maximum polarization is about 11 μC/cm2 which is measured after 104 cycles and stable up to 106 cycles. The influence of the layer thickness on the oxide properties is investigated for 10–40 nm thick HfLuO; however, a thickness dependence of the ferroelectric properties is not observed.
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