Magnetic Properties of Quasi-Two-Dimensional Ruthenates Studied by Mean Field Theoretical Approach

We discuss magnetic properties of quasi-two-dimensional ruthenates within mean field theory. By applying the mean field approximation to simple two-dimensional three-band model, we investigate the possibility of magnetic ground states in quasi-two-dimensional ruthenates and construct magnetic phase diagrams at zero temperature. Then we calculate the paramagnetic spin susceptibility, using the random phase approximation. We discuss what can be an important cause of ferromagnetic properties in quasi-two-dimensional ruthenates, focusing particularly on the effect of Hund's coupling. Consequently we point out the importance of the van Hove singularity originating from the Ru4d x y orbital, while we obtain the conclusion casting doubt on the importance of Hund's coupling for the ferromagnetic properties.