XAFS understanding of "repeated" magnetic compensation in Nd0.8Tb0.2Al2

Abstract

Magnetic compensation (zero-moment) has important advantage in spintronics as it does not generate any self stray magnetic field. The physics of magnetic compensation (at a well defined temperature Tcomp) is well understood in terms of competition and compensation between antiferromagnetically coupled magnetic moments of two rare earth ions. The different thermal evolution of the dissimilar rare earth moments can compensate each other at a particular temperature determined by the concentration of the dopant. We have observed, for the first ever time, "repeated" magnetic compensation in both polycrystalline and single crystals of Nd0.8Tb0.2Al2 (Tf1 ~ 86 K and Tf2 ~ 34 K). A possible reason could be the non-random distribution of magnetic rare earth ions on different crystallographic sites, presenting deviation from mean field like situation. The motivation for XAFS derives from detection of these circumstances. XAFS at Nd, Tb L3 edges reveals that 25% (Nd,Al) anti-site defect exists in Nd0.8Tb0.2Al2. This implies that Nd atoms occupy two different sites. In contrast, Tb preferentially substitutes only one of the Nd sites. The implication of these results upon magnetic compensation is discussed.