Influence of Y and Al co-doping on the crystal structure and magnetic properties of Nd2−xYxFe17−yAly

Abstract

The synergic effects of Y and Al co-doping on the structural and magnetic properties of Nd2−xYxFe17−yAly compounds (0 ≤ x ≤ 1.5, 0 ≤ y ≤ 3.0) have been comprehensively investigated by means of X-ray diffraction, neutron diffraction and magnetic measurement. Rietveld refinements indicate that all the prepared samples crystallize in Th2Zn17-type structure (R3¯m space group). For a given Al content (y), the lattice parameter a, c and unit cell volume V of Nd2−xYxFe17−yAly all decrease linearly with increasing Y concentration while the c/a ratio increases. For a given Y content (x), the lattice parameter a, c and unit cell volume V of Nd2−xYxFe17−yAly all increase linearly with increasing Al content. Al atoms prefer to take 18h sites and completely avoid the 9d sites. For a given Al content, Ms of Nd2−xYxFe17−yAly first increases to a maximum and then decreases with increasing Y content. This is quite different from what's observed in other mixed rare earth systems. For a given Y content, TC of Nd2−xYxFe17−yAly first increases rapidly and then increases slowly with increasing Al content but Ms first increases and then decreases. This can be attributed to the competition between the positive effect resulting from the optimization of bond lengths and the negative effect caused by magnetic dilution of nonmagnetic substituent.