Yueh-Sheng Chiang, Chi-Shun Tu, Pin-Yi Chen, Cheng-Sao Chen, J. Anthoniappen, Yi Ting, Ting-Shan Chan, V.H. Schmidt
Magnetic susceptibility and phonons have been characterized in multiferroic Bi(Fe1−xCox)O3−δ ceramics for x=0.0, 0.05, and 0.10 (BFO100xCo) as functions of temperature. A preferred (100) crystallographic orientation and increasing average oxygen vacancies were observed in BFO5Co and BFO10Co. The Fe and Co K-edge synchrotron X-ray absorptions revealed mixed valences of Fe3+, Fe4+, Co2+, and Co3+ ions in BFO5Co and BFO10Co, which exhibit a ferromagnetic (or ferrimagnetic) phase below room temperature due to appearance of ferromagnetic B–O–B (B=Fe and Co) superexchange interactions. Field–cooled (FC) and zero–field–cooled (ZFC) magnetic susceptibilities exhibit a significant spin-glass splitting below room temperature in BFO5Co and BFO10Co. Two Raman-active phonon anomalies at ~170 K (or 200 K) and ~260 K were attributed to the Fe3+–O–Co3+ and Co3+–O–Co3+ magnetic orderings, respectively. This work suggests that the low-spin Co2+–O–Co2+, Fe3+–O–Fe3+ (or Fe4+), and high-spin Co2+–O–Co2+ superexchange interactions are responsible for phonon anomalies at ~290 (or ~300 K), ~400, and ~470 K (or ~520 K) in BFO5Co and BFO10Co. © 2016 Elsevier Ltd and Techna Group S.r.l.
Graduate Institute of Applied Science and Engineering and Department of Physics, Fu Jen Catholic University, Taipei, 24205, Taiwan; Department of Mechanical Engineering, Ming Chi University of Technology, New Taipei City, 24301, Taiwan; Department of Mechanical Engineering, Hwa Hsia University of Technology, New Taipei City, 23567, Taiwan; Department of Physics, University of San Carlos, Cebu City, 6000, Philippines; National Synchrotron Radiation Research Center, Hsinchu, 30076, Taiwan; Department of Physics, Montana State University, Bozeman, 59717, MT, United States
