Abstract
We synthesized Ca1−xSrxFeO3 containing tetravalent iron Fe4+ with high valence by low temperature heat treatment along with ozone oxidization. We investigated the magnetic properties of perovskite Ca1−xSrxFeO3. The charge disproportionation transition temperature (TCD) of Ca1−xSrxFeO3 was observed from x = 0.0 to 0.6 in the magnetic susceptibility measurements. The decrease in TCD occurs is attributed to deformation of the crystal structure. The metamagnetic transitions with hysteresis were observed in the magnetization curves of all the compositions. The metamagnetic behavior is due to helical magnetism, which means that there are intermediate stable states before magnetization is saturated. In the Sr-rich region with x = 0.8 and 1.0, the saturation magnetization shows forced ferromagnetic order with a value of ∼3.2 μB at high magnetic field, H ∼ 60 T.
Highlights
The perovskite Fe oxides with the formula AFeO3 (A: Ca or Sr) contain high-valence Fe4+.1,2 A perovskite-type CaFeO3 undergoes a metal-insulator transition and structural transition from orthorhombic to monoclinic at 290 K.5 Mossbauer spectroscopy indicated that CaFeO3 undergoes charge disproportionation 2Fe4+ → Fe(4−δ)+ + Fe(4+δ)+(δ : temperature dependence) below 290 K.6In contrast, SrFeO3 has a perovskite cubic lattice structure and displays metallic conductivity
In the temperature range above T N, a bending of the magnetic susceptibility corresponding to the charge disproportionation transition temperature T CD is observed
T CD shifted towards low temperature with increase in the doping amount of Sr and was observed until x = 0.6. This result is consistent with the fact that charge disproportion is not observed in SrFeO3,8 indicating that it disappears near the composition with x = 0.6
Summary
Study of the electronic structure of Journal of Applied Physics 97, 10A312 (2005); https://doi.org/10.1063/1.1854275 Tuning the electronic properties of epitaxial strained CaFeO3−δ thin films Applied Physics Letters 114, 221907 (2019); https://doi.org/10.1063/1.5098025
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