Projected iron moments in UFe4Al8 investigated with monochromatic polarized Mossbauer radiation

UFe4Al8 was investigated using a monochromatic, circularly polarized Mossbauer source. The measurements are sensitive to the sign of the hyperfine magnetic field. The iron magnetic moment component along the direction of the applied magnetic field was determined. Quantitative analysis shows that the configuration of iron moments is not collinear and, on average, only about one fourth of the atomic iron moment contributes to the total magnetization in a randomly oriented powder exposed to a held of 1 T at a temperature of 12 K. The presence of ferromagnetic clusters in an otherwise antiferromagnetic ordering is discussed. The conclusions regarding the magnetic structure are compared with the results of powder neutron diffraction experiments. In the course of the interpretation of latter, the Debye temperature theta(D) = 421(13) K was determined.