Atomic occupancy preference of Ga and Ti and its effect on the Mn spin arrangements in YMn6Sn6: Evidence from119Sn Mössbauer spectroscopy

The effects of Ga and Ti substitutions for Sn on the Mn spin arrangements in the YMn6Sn6 compound have been investigated by means of X-ray diffraction (XRD), magnetization measurement and Mössbauer spectroscopy. XRD refinement indicates that Ga and Ti atoms prefer to occupy 2d and 2e sites, respectively. Mössbauer spectra indicate incommensurate magnetic structures for the YMn6Sn6, YMn6Sn5.4Ga0.6 and YMn6Sn5.4Ti0.6 compounds. The substitution of Ga for Sn at the 2d sites is found to significantly decrease the turn angle in the Mn-Sn3-Sn2-Sn3-Mn layer and to subsequently increase the net magnetization. On the other hand, the substitution of Ti for Sn at 2e sites increases the turn angles in the Mn-(Y,Sn1)-Mn and Mn-Sn3-Sn2-Sn3-Mn layers, and consequently decreases the exchange coupling of Mn-Mn between different layers. The resulting ferromagnetic and ferrimagnetic behavior, as has been observed for YMn6Sn5.4Ga0.6 and YMn6Sn5.4Ti0.6, respectively, can be explained in terms of these spin interactions.