Understanding of negative magnetization in DyFe₅Al₇: a neutron diffraction study

In the present study, we have investigated magnetic properties of DyFe₅Al₇ (DFA) compound using neutron diffraction technique. DFA is a ferrimagnetic compound with magnetic ordering temperature (T_C) ~ 240 K. Interestingly, this compound exhibits an interesting and novel phenomenon, called negative magnetization (NM) with compensation temperature (T_COMP) of ~ 93 K. The Rietveld refined neutron diffraction (ND) patterns at some of the selected temperatures are indicated in the article. Refinement of ND data in paramagnetic phase (300 K) reveals that Dy atom occupy 2a crystallographic position, Fe occupy 8f, Al occupy 8i, while 8j site is shared by both Fe and Al atoms. Magnetic moment of atoms i.e. M_Dy(_2a), MFe_(8j) and MFe_(8f) increases with decreasing temperature. Thus, it is role of different rate of change of magnetic moment along with finite MFe_(8j) in inducing NM phenomenon in the present DFA compound; no such phenomenon is present in DyFe₄Al₈ compound where no such Fe occupy 8j crystallographic position