Magnetic and structural properties of the solid solution CuAl2(1−x)Ga2xO4

Abstract

CuAl₂O₄ is a ternary oxide spinel with Cu²⁺ ions ($s=1/2$) primarily populating the A-site diamond sublattice. The compound is reported to display evidence of spin glass behavior but possess a non-frozen magnetic ground state below the transition temperature. On the other hand, the spinel CuGa₂O₄ displays spin glass behavior at ~ 2.5 K with Cu²⁺ ions more readily tending to the B-site pyrochlore sublattice. Therefore, we investigate the magnetic and structural properties of the solid solution CuAl_2(1-x)Ga_2xO₄ examining the evolution of the magnetic behavior as Al³⁺ is replaced with a much larger Ga³⁺ ion. Our results show that the Cu²⁺ ions tend to migrate from tetrahedral to octahedral sites as the Ga³⁺ ion concentration increases, resulting in a concomitant change in the glassy magnetic properties of the solution. Results indicate glassy behavior for much of the solution with a general trend towards decreasing magnetic frustration as the Cu²⁺ ion shifts to the B-site. However, the $x=0.1$ and 0.2 members of the system do not show glassy behavior down to our measurement limit (1.9 K) suggesting a delayed spin glass transition. We suggest that these two members are additional candidates for investigation to access highly frustrated exotic quantum states.