Abstract
A systematic study on the magnetic and electrical percolation phenomena of BaTiO3 (BTO)-NiZnF2O4 (NZFO) composite films is presented in this work with the purpose of simplifying the preparation process of high-performance 1–3-type multiferroic composite films. Results show that the percolation threshold of the composite films depends on the macroscopic dimension of the material. The low-dimensional nature of the composite films results in different percolation thresholds with topological transition in vertical and horizontal directions. BTO-NZFO composite films with a grain size of 15 nm and a thickness of 100 nm exhibited a percolation threshold of 0.18 in the normal direction and a percolation threshold of 0.48 in the horizontal direction. In light of this intriguing feature, a novel multiferroic composite film with 1–3 structure and strong magnetoelectric coupling was easily prepared by a 0–3 process via controlling the NZFO content in the region between two percolation thresholds.
Highlights
Multiferroic materials have become a research focus because of their special properties, such as magnetoelectric coupling, and manifested great potential in the application fields of high-density storage and fast multi-state response[1,2,3,4]
The variation in the conductivity of the BTO-NZFO composite films versus NZFO content shown in Fig. 2(b) is a typical evidence of conductivity percolation that usually occurs in the composites composed of the constituents with different conductivities
In low-dimensional BTO-NZFO composite films, the out-of-plane percolation threshold will be lower than the in-plane percolation www.nature.com/scientificreports threshold. This fact implies that the nanowire-like channels connecting the NZFO nanocrystals come into existence in the normal direction instead of the radial direction in the composite
Summary
Multiferroic materials have become a research focus because of their special properties, such as magnetoelectric coupling, and manifested great potential in the application fields of high-density storage and fast multi-state response[1,2,3,4]. Several strong magnetoelectric coupling systems have been reported since 20045–7, and the magnetoelectric coupling mechanisms including exchange bias and interface control of multiferroic materials have been revealed, broadening our knowledge of the intrinsic properties of such systems[8,9,10] Among these mechanisms, the most widely recognized one is the strain coupling mechanism proposed by Eerenstein and Thiele[11,12], in which strain transmission between lattices can control the magnetic/electrical properties of the material under external electric/magnetic fields. The ferroelectric-ferromagnetic composite films lies in the region between the two percolation thresholds of 2D and 3D systems This is only a theoretical assumption that needs to be verified experimentally. A novel way of preparing multiferroic composites with excellent performance by a simple process was verified
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