Two-step magnetic ordering into a canted state in ferrimagnetic monoclinic Mn${}_3$As${}_2$

Abstract

We report the magnetic structure of room-temperature-stable, monoclinic Mn${}_3$As${}_2$ at 3 K and 250 K using neutron powder diffraction measurements. From magnetometry data, the Curie temperature of Mn${}_3$As${}_2$ was confirmed to be around 270 K. Calorimetry analysis showed the presence of another transition at 225 K. At 270 K, Mn${}_3$As${}_2$ undergoes a $k=0$ ferrimagnetic ordering in the magnetic space group $C2/m$ (#12.58) with Mn moments pointing along $b$. Below 225 K, there is a canting of Mn moments in the $ac$ plane which produces a multi-$k$ non-collinear magnetic structure in space group $C2/c$ (#15.85). The components of Mn moments along $b$ follow $k=0$ ordering and the components along $a$ and $c$ have $k=[00\frac{1}{2}]$ propagation vector. The change in the magnetic ground state with temperature provides a deeper insight into the factors that govern magnetic ordering in Mn-As compounds.

6 pages, 6 figures, 1 table