Magnetic ordering in the nano-laminar ternary Mn2AlB2 using neutron and X-ray diffraction

Abstract

Abstract The nano-laminar ceramic Mn2AlB2 belongs to the orthorhombic M2AlB2 system (M = Cr, Fe, Mn), in which Fe2AlB2 was shown to be ferromagnetic near room temperature. Herein, the magnetic state of Mn2Al11B2 is investigated using magnetization measurements, in the 5–360 K temperature range, X-ray diffraction in the 300–800 K range and neutron diffraction in the 1.6–300 K range. From the totality of our results we conclude that below ∼390 K Mn2AlB2 becomes a canted antiferromagnet. The crystallographic unit cell is doubled along the c axis (i.e. a propagation vector of 0,0,1/2) and the ordered Mn magnetic moments are oriented either along the a or the b axes, with a magnetic moment reaching 0.71(2) µB per Mn atom at 1.6 K. This magnetic structure is in excellent agreement with, and contributes to the validity of the recently reported theoretical calculations for the (Fe1−xMnx)2AlB2 system.