Magnetic and transport properties of R(Mn, In)2 (R—rare-earth metals) with AlB2-structure type

We studied the crystal structure and magnetic properties of ternary rare-earth R(Mn,In)2 compounds (R=Y, La, Ce, Tb–Tm, Lu), which crystallize in the AlB2-structure type with approximate stoichiometry RMn0.67In1.33, but adopting a variable Mn deficiency. YMn0.92In1.08 orders antiferromagnetically below TN ≈ 247 K, CeMn0.65In1.35 is ferromagnetic with TC=134 K. The compounds with magnetic rare earths tend to a glassy magnetic state, presumably due to the disorder in the Mn/In sublattice together with competing exchange interactions. The disorder has also a dramatic impact on the temperature dependence of the electrical resistivity, which is rather flat due to a strong scattering. The absence of long-range order was proved also by specific-heat measurements. Hydrogen absorption, tested for several compounds, led to the synthesis of LaMn0.49In1.51H0.75(5).