Change in the magnetic structure of (Bi,Sm)FeO3 thin films at the morphotropic phase boundary probed by neutron diffraction

Abstract

We report on the evolution of the magnetic structure of BiFeO 3 thin films grown on SrTiO 3 substrates as a function of Sm doping. We determined the magnetic structure using neutron diffraction. We found that as Sm increases, the magnetic structure evolves from a cycloid to a G-type antiferromagnet at the morphotropic phase boundary, where there is a large piezoelectric response due to an electric-field induced structural transition. The occurrence of the magnetic structural transition at the morphotropic phase boundary offers another route towards room temperature multiferroic devices.As one of the only single-phase multiferroic materials with ferroelectric and magnetic transition temperatures well above room temperature, BiFeO 3 (BFO) has been extensively studied. It possesses a robust ferroelectric polarization which is closely tied to its rhombohedral structure, and microstructural properties of BFO thin films (such as the stress state, grain size and its orientation, etc.) can sensitively affect its local ferroelectric properties. Magnetoelectric coupling between the local ferroelectric polarization and magnetism inside BFO thin films can serve as the basis for heterostructured multiferroic devices, 1,2 but their antiferromagnetic properties are known to display complex variations depending delicately on the local microstructural properties. We have previously used neutron diffraction to probe the nature of antiferromagnetic domains in epitaxial BFO thin films. 3,4 Chemical substitution in BFO has been explored in order to improve the ferroelectric, piezoelectric, and dielectric properties of the material. [5][6][7][8] It has been demonstrated that the substitution of rare earth elements into the A-site of BFO thin films results in a structural phase transition from a ferroelectric rhombohedral phase to a paraelectric orthorhombic phase. 9,10,11 In the case of Sm the transition occurs at ~14% doping 12 at which point films exhibit a Morphotropic Phase Boundary (MPB). Earlier studies showed that in the vicinity of the MPB, an electric field can be used to drive the transition from the paraelectric orthorhombic phase to the rhombohedral ferroelectric phase, resulting in a very large piezoelectric effect d 33

Performance Enhancement of Flexible Piezoelectric Nanogenerator via Doping and Rational 3D Structure Design For Self‐Powered Mechanosensational System

“…According to previous reports, doping is a simple and effective means to ameliorate the piezoelectric properties of BFO, such as Mn, Sm, La, and Ti . Figure a indicates the X‐ray diffraction (XRD) patterns of Bi 1− x Sm x Fe 1− x Ti x O 3 (0 ≤ x ≤ 0.16), from which small traces of secondary phase are labeled by .…”

Micro‐to‐nano domain structure and orbital hybridization in rare‐earth‐doped BiFeO3 across morphotropic phase boundary

“…29 A magnetic transition from a spin cycloid to a Gtype AFM ordering was reported in (Bi 1Àx Sm x )FeO 3 ceramics at x~0.14. 30,31 The magnetization was enhanced remarkably upon the composition-driven transition from rhombohedral to orthorhombic phase. [30][31][32][33] The dielectric result suggests that the N eel temperature (T N ) decreases in (Bi 1Àx Sm x )FeO 3 ceramics with increasing Sm.…”

“…30,31 The magnetization was enhanced remarkably upon the composition-driven transition from rhombohedral to orthorhombic phase. [30][31][32][33] The dielectric result suggests that the N eel temperature (T N ) decreases in (Bi 1Àx Sm x )FeO 3 ceramics with increasing Sm. 34 Phase transition, polarization, and electromechanical responses are critical phenomena in FE materials in the vicinity of the MPB.…”

“…A phenomenological model was used to describe the temperature‐composition phase diagram and predicated a FE‐AFE and an AFE‐paraelectric (PE) transitions at x ~0.1 and ~0.16, respectively . A magnetic transition from a spin cycloid to a G‐type AFM ordering was reported in (Bi 1− x Sm x )FeO 3 ceramics at x ~0.14 . The magnetization was enhanced remarkably upon the composition‐driven transition from rhombohedral to orthorhombic phase .…”

Raman vibrations and photovoltaic conversion in rare earth doped (Bi0.93RE0.07)FeO3 (RE=Dy, Gd, Eu, Sm) ceramics

“…Previous studies of doped BFO materials have focused on the structural and magnetic properties [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25]. The (Bi 1 À x La x ) FeO 3 ceramics have a rhombohedral R3c symmetry for x r 0.125 [18].…”