Structural and magnetic properties of oxide films

In search of a magnetic oxide, which is insensitive to oxygen at interfaces and thus appropriate as an electrode layer for tunneling junction applications, we prepared thin films of $\chem{CoFeHfO}$ by reactive DC-magnetron sputtering technique and investigated the relation between structural and magnetic properties. The results suggest that the films consist of two disorded phases, a $\chem{Co(Fe)}$-rich and a $\chem{HfO}$-rich. It was found that the degree of film homogeneity and thus the magnetic nature depends on preparation conditions such as film thickness and deposition rate. A second magnetic phase with a high saturation field, which is present in thicker films, could therefore be reduced by decreasing the film thickness. Consequently, the thinnest film (10$\un{nm}$) is nearly single phased and exhibits an excellent uniaxial anisotropy with a coercive field $H_{\ab{c}}$ of 16$\un{Oe}$ along the easy axis. Additionally, thermomagnetic measurements were carried out to understand annealing-induced effects. A clear improvement with increased saturation magnetisation ($M_{\ab{s}}=695$$\un{emu/cm^{3}}$) and decreased $H_{\ab{c}}$ was observed, which can be attributed to structural relaxation and phase separation caused by annealing