Crystal and magnetic properties of U(Mn1−xFex)2Si2

Abstract

The solid solution system U(Mn_1−xFe_x)₂Si₂ (0 ⩽ x ⩽ 1) was synthesized by direct melting of the UMn₂Si₂ and UFe₂Si₂ components and investigated by X-ray diffraction, magnetometric and Mössbauer effect methods. The series investigated behaves similarly in many respects to the isostructural ones formed with other elements. The values of the lattice constants obey Vegard's law. The isomer shift and quadrupole splitting vary gradually across the range of iron concentration. The quadrupole splitting reflects a deviation from the ideal tetrahedral coordination of iron site neighbours. The manganese-rich samples (x ⩽ 0.3) were found to be ferromagnets at 78 K while the others behave as Pauli paramagnets above 78 K. The Curie temperature and hyperfine magnetic field decrease strongly with increasing iron concentration. The composition dependence of the Curie temperature is well described by the Heisenberg model in which the magnetic interactions between nearest neighbours and the uniaxial magnetic anisotropy were taken into account.