Layer Effects on the Magnetic Behaviors of Aurivillius Compounds Bi _{n +1} Fe _{n −3} Ti ₃ O _{3 n +1} ( n = 6, 7, 8, 9)

Abstract

Bi n +1 Fe n −3 Ti 3 O 3 n +1 (BFT‐ n , n = 6, 7, 8, 9) ceramics were prepared using Pechini's method and their magnetic behaviors were investigated. XRD and HRTEM results suggested that BFT‐ n have the pure Aurivillius structure. Magnetic properties of BFT‐ n depend largely on their layer numbers. BFT‐6 exhibits a paramagnetic (PM)‐like characteristics with a small portion of weak antiferromagnetic (AFM) property; while spin glass (SG)‐like characteristics was observed for the BFT‐ n ( n ≥ 7) samples. An amazing exchange bias phenomenon was observed in BFT‐ n ( n ≥ 7) ceramics, of which shifts in both vertical and horizontal direction were found in the magnetic hysteresis loops as the functions of testing temperature and the layer number ( n ). For BFT‐8, the maximum H E is 3911 Oe when measured at 5 K. The AFM/SG interface should be the origin for the observed exchange bias effect, which was aggravated with the increased layer numbers for the enhanced coupling probability among Fe 3+ ions. The fantastic exchange bias behavior of BFT‐ n ( n ≥ 7) makes them a good single‐phase candidate for future spintronic devices.