An elastic Ising model for a one-dimensional diatomic spin chain is proposed to explain the ferroelectricity induced by the collinear magnetic order with a low-excited energy state. A statistical theory based on this model is developed to calculate the electrical and magnetic properties of Ca3CoMnO6, a typical quasi-one-dimensional diatomic spin chain system. The calculated ferroelectric polarization and dielectric susceptibility show a good agreement with recently reported data on Ca3Co2-xMnxO6 (x≈0.96) (Phys. Rev. Lett. 100 047601 (2008)), although the predicted magnetic susceptibility does not coincide well with experiment. We also address the rationality and deficiency of this model by including a first-order correction which improves the consistency between the model and experiment.
Sol-gel process was adopted to prepare BiFeO3 films.BiFeO3 films were deposited on LaNiO3 coated Si(100) substrates annealed at 500 and 550 ℃,respectively.The X-ray diffraction results reveal that BiFeO3 film has a rhombohedrally distorted perovskite structure with space group R3c.The film annealed at 500 ℃ has larger remnant polarization(Pr) of 35.3 μC/cm2.For the film annealed at 550 ℃,smaller remnant polarization of Pr=4.8 μC/cm2 is observed for its low breakdown electric field.Lower leakage conduction is observed in the film annealed at 500 ℃ at low applied field.
We have investigated the low-temperature magnetism and spin-lattice coupling in (Bi 0.46 Na 0.46 Ba 0.08)TiO 3:Co in order to understand the magnetoelectric effect in such artificially synthesized dilute magnetic ferroelectrics.It is revealed that the as-prepared (Bi 0.46 Na 0.46 Ba 0.08)TiO 3:Co at Co content of 20%～30% exhibits fascinating ferrimagnetism which is robust against magnetic field,the abnormal spin-lattice coupling characterized by a negative magnetostriction effect;and the suppressed magnetic moment within the temperature range of 30 K～50 K is identified.These magnetic behaviours at low temperatures can be explained by the competition between the ferrimagnetic response and the magnetic moment suppression induced by the abnormal spin-lattice coupling effect.Finally,the ferroelectric and magnetodielectric properties are also discussed.
