  We address the problem of orientational order in frustrated interaction
systems as a function of the relative range of the competing interactions. We
study a spin model Hamiltonian with short range ferromagnetic interaction
competing with an antiferromagnetic component that decays as a power law of the
distance between spins, $1/r^\alpha$. These systems may develop a nematic phase
between the isotropic disordered and stripe phases. We evaluate the nematic
order parameter using a self-consistent mean field calculation. Our main result
indicates that the nematic phase exists, at mean-field level, provided
$0<\alpha<4$. We analytically compute the nematic critical temperature and show
that it increases with the range of the interaction, reaching its maximum near
$\alpha\sim 0.5$. We also compute a corse-grained effective Hamiltonian for
long wave-length fluctuations. For $0<\alpha<4$ the inverse susceptibility
develops a set of continuous minima at wave vectors $|\vec k|=k_0(\alpha)$
which dictate the long distance physics of the system. For $\alpha\to 4$,
$k_0\to 0$, making the competition between interactions ineffective for greater
values of $\alpha$.
