| Abstrakt: |
Corundum and related compounds possess interesting properties for functional applications, such as magnetization reversal or linear magneto electricity, depending on their structures and magnetic ground states. In this system, materials corresponding to the A4Nb2O9formula crystallize in two different structures, i.e., Pbcnfor Ni4Nb2O9and P3̅c1 for A= Co, Fe, and Mn, leading to ferrimagnetism and antiferromagnetism at low temperature, respectively. In this family, the nickel-based compound is special because Ni4Nb2O9is the only one crystallizing in the orthorhombic structure. The Pbcnand P3̅c1 structures are both able to adapt to various substitutions of the A-cation, and as soon as Ni is involved, the two structural types are stabilized depending on the Ni/Aratio and A. In this context, the differences reported in the structural and magnetic behaviors of the Ni4–xCoxNb2O9and Ni4–xZnxNb2O9series motivated the (Ni/Co/Zn)4Nb2O9study by mapping the magnetization-structure-composition phase diagram. This first step toward compositionally complex materials allows us to identify an unexpected large area of compounds that exhibit ferrimagnetism and magnetization reversal. Moreover, inside this domain, interesting variations of Néel temperature and compensation temperature are observed, including an increase of Tcompinduced by nonmagnetic substituting cations. The originality of these structural and magnetic behaviors makes these materials promising for theoreticians to provide conceptual models, especially since the partial substitution of the magnetic cation by a d0one may enhance the magnetization reversal. |
