In order to improve the multiferroic properties of BiFeO3 (BFO), partial substitution of the A site for Bi has been reported to effective method. Last decade, two classes of dopants used include rare earth elements (R), such as Y, La, Nd, Pr, and Sm (1), and alkali earth elements, e.g. Ca, Sr, and Ba (2). These dopants could reduce the leakage current density and improve the ferroelectric as well as magnetic properties of BFO. Although the investigations on multiferroic properties of R-doped BFO are extensive, BFO doped with heavy rare earth (H) is less discussed. To substitute H, such as Gd, Tb, Dy, Ho, and Er, for Bi in BFO is expected to improve the magnetic properties because the larger magnetic moment (7.8-10.6 μB) for H ions may introduce an additional magnetic interactions and ordering in BFO (3). In this work, we adopted pulsed laser deposition (PLD) to develop Bi0.9H0.1FeO3 (BHFO) films on glass substrates. The microstructure, ferroelectric, and magnetic properties of BHFO films are studied. BHFO films were confirmed to mainly consist of the perovskite phase. The desired multiferroic properties with the suppressed leakage is reached. The magnetic properties with the enhanced magnetization are found for BHFO films: their Ms are 18.8, 18.9, 21.3, 25.6, 18.5 emu/cm3, for the films with H = Gd, Tb, Dy, Ho, and Er, respectively. The higher magnetic moment of H ion is, and larger Ms of the films is. The above behavior reveals magnetization of BFO films with H substitution is mainly dominated by the magnetic moment of H ion. Besides, good ferroelectric properties are also attained for BHFO films, where the largest remanent polarization (2Pr) of 120.1 µC/cm2 is achieved for H = Gd, related to low leakage and high BHFO(110) texture. It might be related to the larger ionic radius for Gd than other H. Relationship between leakage mechanisms and microstructure are also discussed in those BHFO films.
(1) D. Kan et al., J. Appl. Phys. 110, 014106 (2011).
(2) H.W. Chang et al., J. Alloys Compd. 683, 427 (2016).
(3) N. Jeon et al., Appl. Phys. Lett. 98, 072901 (2011).