Tunable magnetism and structural transformations in mixed light- and heavy-lanthanide dialuminides

Rare-earth intermetallics play a critical yet often obscure role in numerous technological applications, including sensors, actuators, permanent magnets, and rechargeable batteries; therefore, understanding their basic science is of utmost importance. Here we report structural behaviors, specific heat, and magnetism of Pr1-xErxAl2 studied by means of temperature-dependent x-ray powder diffraction, heat capacity, and magnetization measurements, in addition to first-principles calculations. Although the cubic lattice of PrAl2 distorts tetragonally at the Curie temperature TC, the distortion is rhombohedral in ErAl2, creating a potential for instability in the pseudobinary PrAl2-ErAl2 system. When 0.05≤x≤0.5, materials show complex magnetization behaviors, including metamagnetic transitions and Griffith-like phase. Unique among other mixed-lanthanide dialuminides, the substitution of Er for Pr in Pr1-xErxAl2 results in unexpected ferrimagnetic behavior, and the ferrimagnetic interactions become strongest around x=0.25, where the compound shows unusual metamagnetic like transitions observed only in the odd-numbered quadrants of the full magnetic field cycles. The electronic structure calculations, including exchange interactions and crystal field splitting, magnetic moments, anisotropic 4f energy density, and magnetic surface potentials rationalize the interesting physics observed experimentally.