Magnetization densities in UPtAl: Experimental and theoretical study

UPtAl crystallizes in the ZrNiAl-type hexagonal structure and orders ferromagnetically with uranium magnetic moments parallel to the c axis below 43 K. We present the results of a polarized neutron experiment on a UPtAl single crystal and electronic structure calculations. The experimental data were analyzed by the maximum entropy method and within the atomic model. The main magnetic contribution originates from the uranium atoms. The ratio - μ L /μ S between the orbital and spin uranium mornent is reduced in coomparison to the free ion value, indicating a delocalization of the uranium 5 f states. It remains unchanged between I and 9.6 T. Induced magnetic moments are observed on both platinum sites (within the U-Pt and Al-Pt layers). An additional magnetization density is observed around the aluminum positions. The first-principles electronic structure calculations were performed in the framework of the density functional theory and confirmed the ferromagnetic state. The calculated and experimental magnetic moments are compared and the results discussed in the context of the previous studies on isostructural UTX compounds.