  We investigate theoretically the spin-spin interaction of two-electrons in
vertically coupled QDs as a function of the angle between magnetic field and
growth axis. Our numerical approach is based on a real-space description of
single-particle states in realistic samples and exact diagonalization of
carrier-carrier Coulomb interaction. In particular, the effect of the in-plane
field component on tunneling and, therefore, spin-spin interaction will be
discussed; the singlet-triplet phase diagram as a function of the field
strength and direction is drawn.
