Abstract
The interplay among ferroelectric, magnetic and elastic degrees of freedom in multiferroics is the key issues in condensed matters, which has been widely investigated by various methods. Here, using ultrafast two-color pump-probe spectroscopy, the picosecond electron-phonon and spin-lattice coupling process in Dysprosium doped-BiFeO3 (BDFO) films on SrTiO3 (STO) substrate have been investigated systematically. The Dy-doping induced structural transition and magnetic enhancement in BDFO is observed by ultrafast electron-phonon and spin-lattice interaction, respectively. The elastic anomalies in BDFO films are revealed by the photo-induced coherent acoustic phonon. With increasing the Dy doping ratio, the frequencies of the acoustic phonon in the films are modulated, and the phonon transmission coefficient between films and substrate is found to approach unity gradually. The ultrafast observation of the tunability of the ferroelectric, magnetic and the elastic properties in the morphotropic phase boundary of rare-earth doped BFO films provides new insights into the integration of BFO in next-generation high frequency electro-magnetic and electroacoustic devices.
Highlights
As a monophase multiferroic, bismuth ferrite (BFO) shows coexistence of both antiferromagnetic and ferroelectric behavior at room temperature, which had been widely investigated in the past decade[1,2,3]
It’s reported that by means of dysprosium substitution, the crystal structure of BFO films could be modulated from rhombohedral to orthorhombic, which could result in the releases of the compressive strain introduced by the mismatch between the BFO film and SrTiO3 (STO) substrate[21]
Ultrafast pump-probe spectroscopy is employed to investigate a series of BixD1−xFeO3 (BDFO) thin films, the ultrafast dynamics of electron-lattice and spin-lattice response is found to be sensitive to the phase transition around the critical point, a sub-picosecond electric fields applied to films for generating ultrafast coherent acoustic phonons, 1State Key Laboratory of High Field Laser Physics, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai, 201800, China. 2Department of Physics, Shanghai University, Shanghai, 200444, China. 3School of Materials Science and Engineering, Nanyang Technological University, Singapore, 639798, Singapore
Summary
Bismuth ferrite (BFO) shows coexistence of both antiferromagnetic and ferroelectric behavior at room temperature, which had been widely investigated in the past decade[1,2,3]. The ultrafast electron-magnon coupling and giant ultrafast photo-induced strain were reported in BFO17, which draws new insight into the ultrafast electric-magnetic-elastic coupling in this type of material. Ultrafast spectroscopy has been employed to investigate the complicated phase transition and coupling among electron, lattice and spin subsystem in multiferroics, which shows possible magnetoelectric coupling occurring at the vicinity of the transition temperature[18]. Ultrafast pump-probe spectroscopy is employed to investigate a series of BixD1−xFeO3 (BDFO) thin films, the ultrafast dynamics of electron-lattice and spin-lattice response is found to be sensitive to the phase transition around the critical point, a sub-picosecond electric fields applied to films for generating ultrafast coherent acoustic phonons, www.nature.com/scientificreports/ Figure 1. Which shows the ultrafast piezoresponse softening behavior at the phase boundary These results shed a new light on the chemical and strain engineering of the ultrafast electromechanical coupling in BFO films
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