The disordered and correlated insulator Bi2CrAl3O9
Abstract
The 3 d transition metal insulator Bi2CrAl3O9 forms with a quasi-one-dimensional structure characterized by linear chains of edge-sharing, Cr-and Al-centered, distorted octahedra. The UV/Vis spectrum of high-quality single crystals is marked by broad absorption edges corresponding to direct transitions across a 1.36-eV insulating gap. Measurements of dc magnetic susceptibility χ reveal a fluctuating moment of 2.60 ±0.01 μB/Cr —reduced from the 3.87 μB/Cr expected for Cr3 +, while the Weiss temperature ΘW=-21 ±1 K implies that the prevailing local moment interactions are weakly antiferromagnetic in nature. Some 10% of the fluctuating moment is quenched, presumably due to the onset of an antiferromagnetic or spin glass phase at temperature T★=98 ±3 K, while measurements of magnetization versus field H at T ≤10 K scale as H /T0.68 (4 ) , suggesting the presence of quantum fluctuations associated with a disordered phase. Density functional theory calculations carried out within the generalized gradient approximation are in excellent agreement with experimental results, asserting that short-range magnetic interactions remnant above T★ stabilize the insulating state.
- Publication:
-
Physical Review B
- Pub Date:
- September 2019
- DOI:
- 10.1103/PhysRevB.100.104425
- Bibcode:
- 2019PhRvB.100j4425U