Magnetic Moment of MnSi

MnSi is a metallic helimagnet below 29 K. Density functional theory predicts that it has a moment of 1.0 $\mu_B$/Mn, which is much larger than the measured value of ~0.4 $\mu_B$/Mn. By adding a Hubbard-U correction, we have found a ground state with a moment consistent with the experimental value. These solutions posess a novel quadrupolar spin ordering. We discuss their behavior under pressure and in a magnetic field.