Magnetic Structure Transitions inLixMn1−xSe

The magnetic structures occurring in lithium-substituted manganese selenide (${\mathrm{Li}}_x{\mathrm{Mn}}_{1-x}\mathrm{Se}$) have been examined by low-temperature powder neutron diffraction measurements. The composition with $x=0.05\mathrm{}$ retains the fcc ordering of the second kind found in MnSe, the transition temperature being lowered to 83°K. For $x=0.07\mathrm{}$ the same type of ordering sets in at 73°K, but the spin direction changes abruptly as the temperature is lowered through 45°K; furthermore, the superlattice intensities decrease when an external magnetic field is applied along the scattering vector. At $x=0.10\mathrm{}$, the spontaneous moment observed at 77°K by magnetization measurements is shown to be ferromagnetic, again by means of an external field, and a transition is found at 71°K from ferromagnetism to antiferromagnetism with the third kind of ordering. The results are discussed with relation to models containing canted spins and multiple antiferromagnetic axes.