Charge Density Wave Accompanied by Spin Density Wave in Mn3Si

The displacement modulation due to the charge density wave (CDW) in Mn3Si, which occurs as second harmonics of the spin density wave (SDW), has been investigated by synchrotron x-ray diffraction and the existence of CDW below Neel temperature of 23 K has been confirmed. High resolution measurement revealed the splitting of the satellite peaks deviating very little from the [111] axis toward [110] direction, suggesting the possibility of a single or double q CDW state. The temperature dependence of the satellites indicates the existence of the phase transition at T-t = 8.5 K, in agreement with the neutron diffraction result [Phys. Rev. B 73, 224416 (2006)]. The analysis of reflection intensities using a single q model, which is a limiting case of no splitting, shows that in both phases Si and Mn-II have larger displacement than that of Mn-I. The formation of single and double q SDWs and their nesting mechanism are discussed.