Chrome Extension
WeChat Mini Program
Use on ChatGLM

Coexistence of large negative and positive magnetodielectric response in Bi1-xCaxFe1-yTiyO3-delta nanoparticle ceramics

PHYSICAL REVIEW B(2021)

Cited 7|Views3
No score
Abstract
Magnetodielectric (MD) properties of as-prepared (AP) and air-annealed Bi1-xCaxFe1-yTiyO3-delta nanoparticle ceramics made by spark plasma sintering process are investigated as a function of temperature. Aliovalent Ca2+ substitution at Bi3+ site creates oxygen vacancies (V-O) in the lattice disrupting the intrinsic spin cycloid of BiFeO3, which are suppressed when the charge compensating Ti4+ is co-substituted. In addition, cation substitution reduces the grain size and increases surface oxygen vacancies. These lattice and surface V-O defects play a significant role in enhancing the magnetic properties. Zero-field-cooled magnetization curves of all AP samples show a sharp Verwey-like transition at similar to 120 K, which weakens on air-annealing. A coexistence of positive and negative MD [MD = Delta epsilon(H)/epsilon(H=0); Delta epsilon(H) = epsilon(H) - epsilon(H = 0)] response is observed, with the former dominating at 300 K and the latter at 10 K. As-prepared 5 at.% (10 at.%) Ca and Ca-Ti substituted BiFeO3 ceramics exhibit a maximum MD response of -10% (similar to+3%) at 10 K (300 K). NegativeMD response diminishes for air-annealed Bi1-xCaxFe1-yTiyO3-delta ceramics due to the reduction in V-O concentration. Samples exhibiting dominant positive MD response show a similar trend for MD vs H and M-2 vs H plots. This agreement between M-2 and Delta epsilon(H) demonstrates a strong inherent MD coupling. On the contrary, negative MD does not follow this trend yet shows a linear relationship of MD vs M-2, suggesting a strong coupling between the magnetic and dielectric properties. Temperature-dependent MD studies carried out at 5 T show a gradual change from negative to positive values. Negative MD at low temperatures could be activated by the spin-lattice coupling, which dominates even at high frequency (1 MHz) under the applied field. Other contributions, including Verwey-like transition, magnetoresistance, and Maxwell-Wagner effects, do not influence the observed MD response. A prominent role of oxygen vacancies in altering the MD behavior of BiFeO3 is discussed in detail.
More
Translated text
AI Read Science
Must-Reading Tree
Example
Generate MRT to find the research sequence of this paper
Chat Paper
Summary is being generated by the instructions you defined