Exchange coupling and improved properties of the multilayer CoFe2O4/La0.7Sr0.3MnO3 thin films

Abstract

Hard/soft interface plays a role in the properties of the composite metal-based magnets, while it is less talked in the composite permanent oxide magnets on the magnetic interaction and properties due to easy interdiffusion. Here, multilayer thin films composed with hard CoFe2O4 phase and soft La0.7Sr0.3MnO3 layers were choose and synthesized without interdiffusion by a chemical solution method. Furthermore, the effects of the annealing temperature and the number of soft layer on the magnetic interaction and properties are investigated. All composite films behavior as one rigidly coupled composite magnet at room temperature, and the magnetic properties increase with increasing annealing temperature. The coercivity and maximum magnetic energy product can respectively reach 8.27 kOe and 2.4 MG Oe at the temperature of 300 K. Exchange coupling was effectively enhanced and even dominate the magnetic interaction with less soft layers for the in-plane direction. Conversely, dipolar interaction predominates, but becomes weak in the composite films with more soft layers and attenuates with increasing annealing temperature for the out-of-plane direction. All of the results suggest that a suitable grain size of the hard phase and an improved interface may be more important for a rigidly coupled composite oxide magnet with good performance.