UNUSUAL MAGNETIC-INTERACTIONS IN COMPOUNDS WITH THE THMN12 STRUCTURE

Neutron diffraction experiments have been performed on single crystals of MFe4Al8 where M = Y, Lu, Dy and U. All compounds hare the ThMn12 b et crystal structure with Fe and Al atoms on separate sites. The Fe su blattice order antiferromagnetically above 100 K with a wave vector (e psilon, epsilon 0), where epsilon = 0.229 for Y and Lu and 0.133 for D y. For UFe4Al8 epsilon = 0 and the U atom is in position of zero-molec ular field from the surrounding Fe atoms. In an applied magnetic field parallel to the easy axis, the U atoms align with the field, but the Fe sublattice has a + - + - antiferromagnetic configuration with momen ts almost perpendicular to the applied field.