The oxygen fugacity(f_(O2)) may affect the ionic conductivity of olivine under upper mantle conditions because Mg vacancies can be produced in the crystal structure by the oxidization of iron from Fe^(2+) to Fe3+. Her...The oxygen fugacity(f_(O2)) may affect the ionic conductivity of olivine under upper mantle conditions because Mg vacancies can be produced in the crystal structure by the oxidization of iron from Fe^(2+) to Fe3+. Here we investigated olivine ionic conductivity at 4 GPa, as a function of temperature, crystallographic orientation, and oxygen fugacity, corresponding to the topmost asthenospheric conditions. The results demonstrate that the ionic conductivity is insensitive to f_(O2) under relatively reduced conditions(f_(O2) below Re-ReO_(2) buffer), whereas it has a clear f_(O2)-dependence under relatively oxidized conditions(f_(O2) around the magnetite-hematite buffer). The ionic conduction in olivine may contribute significantly to the conductivity anomaly in the topmost asthenosphere especially at relatively oxidized conditions.展开更多
Magnetoelectric(ME)materials have caught worldwide attentions owing to their potential technological applications in ME switching devices or high-density data storage.However,realizing a sufficiently strong ME effect ...Magnetoelectric(ME)materials have caught worldwide attentions owing to their potential technological applications in ME switching devices or high-density data storage.However,realizing a sufficiently strong ME effect in one single material is always the key issue.Herein,we systematically investigate the Co_(3)NiNb_(2)O_(9),including the characterization of its crystalline structure,magnetism,specific heat,and pyroelectric properties.It is revealed that Co_(3)NiNb_(2)O_(9) exhibits a remarkable ME response below the magnetic phase transition temperature of TN-32 K.On one hand,the magnetic field-induced electric polarization is observed below TN while it is non-ferroelectric at no magnetic field.The evaluated ME coefficient is as large as 21.2 ps/m.On the other hand,the magnetization is significantly modulated by the applied electric field,with the inverse ME coefficient being 14.1 ps/m.The observed ME responses suggest a stable ME mutual control by the magnetic or electric field in Co_(3)NiNb_(2)O_(9).展开更多
基金financially supported by the annual budget of Bayerisches Geoinstitut to H.Fei and the German Research Foundation (DFG) to T.Katsura (KA3434/3-1,KA3434/3-2,KA3434/7-1,KA3434/8-1,and KA3434/9-1)。
文摘The oxygen fugacity(f_(O2)) may affect the ionic conductivity of olivine under upper mantle conditions because Mg vacancies can be produced in the crystal structure by the oxidization of iron from Fe^(2+) to Fe3+. Here we investigated olivine ionic conductivity at 4 GPa, as a function of temperature, crystallographic orientation, and oxygen fugacity, corresponding to the topmost asthenospheric conditions. The results demonstrate that the ionic conductivity is insensitive to f_(O2) under relatively reduced conditions(f_(O2) below Re-ReO_(2) buffer), whereas it has a clear f_(O2)-dependence under relatively oxidized conditions(f_(O2) around the magnetite-hematite buffer). The ionic conduction in olivine may contribute significantly to the conductivity anomaly in the topmost asthenosphere especially at relatively oxidized conditions.
基金supported by the National Key Research Projects of China[Grant No.2016YFA0300101]the National Natural Science Foundation of China[Grant Nos.12074111,11804088,11704109,51431006]the Research Project of Hubei Provincial Department of Education[Grant No.B2018146].
文摘Magnetoelectric(ME)materials have caught worldwide attentions owing to their potential technological applications in ME switching devices or high-density data storage.However,realizing a sufficiently strong ME effect in one single material is always the key issue.Herein,we systematically investigate the Co_(3)NiNb_(2)O_(9),including the characterization of its crystalline structure,magnetism,specific heat,and pyroelectric properties.It is revealed that Co_(3)NiNb_(2)O_(9) exhibits a remarkable ME response below the magnetic phase transition temperature of TN-32 K.On one hand,the magnetic field-induced electric polarization is observed below TN while it is non-ferroelectric at no magnetic field.The evaluated ME coefficient is as large as 21.2 ps/m.On the other hand,the magnetization is significantly modulated by the applied electric field,with the inverse ME coefficient being 14.1 ps/m.The observed ME responses suggest a stable ME mutual control by the magnetic or electric field in Co_(3)NiNb_(2)O_(9).
