Realization of a classical Ruddlesden Popper type bilayer nickelate in Sr$_3$Ni$_{2-x}$Al$_{x}$O$_{7-δ}$ with unusual Ni$^{4+}$

Hasan Yilmaz; Kathrin Küster; Ulrich Starke; Oliver Clemens; Masahiko Isobe; Pascal Puphal

paper

Realization of a classical Ruddlesden Popper type bilayer nickelate in Sr $_{3}$ Ni $_{2 - x}$ Al $_{x}$ O $_{7 - δ}$ with unusual Ni $^{4 +}$

arXiv:2406.12453

Abstract

The discovery of 80 K superconductivity in bilayer La $_{3}$ Ni $_{2}$ O $_{7}$ at pressures greater than 14 GPa presents a unique opportunity to study a novel class of high-temperature superconductors. Therefore, other bilayer nickelate following the classical ( $T^{4 +}$ ) Ruddlesden-Popper (RP) series of Sr $_{3}$ Ni $_{2}$ O $_{7}$ would present an interesting new candidate. In this work, we study the stabilization of RP $n = 2$ phase in Sr $_{3}$ Ni $_{2 - x}$ Al $_{x}$ O $_{7}$ , via floating zone growth of crystals. With powder and single crystal XRD, we study the stability range of the RP-type phase. Our Thermogravimetric Analysis (TGA), X-ray photoelectron spectroscopy (XPS) and gas extraction studies reveal a remarkably high oxidation state of Ni $^{4 +}$ . The obtained black crystals are insulating in transport and show a magnetic transition around 12 K.

Realization of a classical Ruddlesden Popper type bilayer nickelate in Sr3​Ni2−x​Alx​O7−δ​ with unusual Ni4+

Abstract

Realization of a classical Ruddlesden Popper type bilayer nickelate in Sr $_{3}$ Ni $_{2 - x}$ Al $_{x}$ O $_{7 - δ}$ with unusual Ni $^{4 +}$