Magnetic properties of ThFexAl12-x alloys

The results of magnetic properties of ThFexAl12-x powder samples with iron concentration x = 4, 4.5 and 5, studied by means of X-ray (XD) and neutron diffraction (ND) techniques as well as the Mossbauer spectroscopy with the monochromatic circularly polarised source (MCPMS), and magnetisation measurements using vibrating sample magnetometer (VSM) are presented. Unpolarized neutron diffraction pattern leaves no doubts that the modulated magnetic structure is observed in the tetragonal ThFe4Al8 compound. The interpretation of our neutron data requires the presence of non-zero magnetic propagation vectors different from the nuclear one. ThFe4Al8 sample has double spiral structure with moments rotating in a plane perpendicular to the wave vector q(1) = (q(x), q(x), 0) as well as to q(2) = (0, 0, q(z)). Both of them are temperature independent in the range 1.5 K-70 K. The value of iron magnetic moment is close to 1 mu(B)/Fe atom at 1.5 K.