Commensurate-incommensurate magnetic phase transition in the new Yb1−xLuxMn6Sn6 compounds

We investigate the magnetic properties of the new Yb1−xLuxMn6Sn6 (0.00 ≤ x ≤ 1.00) alloys from AC/DC magnetization and powder neutron diffraction experiments. Room-temperature XANES measurements at Yb L3 edge indicate that Yb is in an intermediate valent state (υYb ∼ 2.6) in the whole Yb1−xLuxMn6Sn6 series. In these compounds only the Mn sublattice magnetically orders with an atomic Mn moment close to mMn ∼2.2 μB at 2 K throughout the series. Lu substitution yields a crossover from ferromagnetism to antiferromagnetism of the Mn sublattice. In RMn6Sn6 compounds, this is the first time that such transition of the Mn sublattice is induced by substitution on the R site. The enhancement of the antiferromagnetic interactions likely results from modification in valence electron concentration since intermediate valent Yb is replaced by trivalent Lu.