The crystal and magnetic structures of the TbNi 2 Mn compound have been refined by the Rietveld analysis of neutron powder-diffraction data. The compound has a cubic C15b-type structure, in which Mn atoms partially occupy both the 4a and 16e sites. Bulk magnetization measurements revealed magnetic ordering below the Curie temperature T C = 142 K. The values of magnetic moment are different for the Tb ion at the 4a and 4c positions. In the 4c site, the Tb moment is determined to be 5.4 B / Tb ion. The low value of the Tb-ion moment is indicative of the formation of a random magnetic anisotropy.

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Specific features of the phase transformation A1 ! L1 0 (space groups Fm3m and P4/mmm, respectively) in single crystals of the equiatomic alloy FePd subjected to annealings both in the absence and in the presence of external uniaxial load, as well as in polycrystalline samples that had undergone severe plastic deformation via high-pressure torsion and subsequent annealing, have been studied. An investigation of the single crystals in a nanostructured state formed at different stages of ordering annealing was performed using optical polarization, thermomagnetic and transmission electron microscopy (TEM) methods. The nanostructured state of the polycrystalline samples FePd after deformation of both disordered and ordered FePd alloys and subsequent annealing was examined with the help of TEM and X-ray techniques. The results obtained were analyzed based on the known concepts of the symmetry theory of phase transitions. It was concluded that the atomic ordering in the FePd alloys is preceded by the formation of a ferroelastic disordered bodycentered tetragonal phase with the structural type A6 and the space group I4/mmm. Experimental data that evidence the existence of a tetragonal disordered phase both in the single crystals and in the polycrystalline samples of FePd after severe plastic deformation and subsequent annealing are reported. Thus, the A1 M A6 M L1 0 phase transformation represents a combination of different types of phase transitions such as cooperative displacement A1 M A6 and ordering A6 M L1 0 of atoms.

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