A-site cation-ordered perovskite cobaltite, RBaCo₂O_x (R = rare earth element), exhibits fascinating physical properties, such as spin-state ordering and high oxygen conductivity, because of the large tetragonal distortion of the Co orbital. However, the distorted coordination geometry prefers oxygen vacancies, resulting in a difficulty in obtaining the stoichiometric phase (x = 6). For example, x in YBaCo₂O_x, which has largely distorted Co orbitals because of the small size of Y³⁺, has so far been limited to 5.52. To expand the available range of x, in this study, we performed a low-temperature topotactic oxidation of YBaCo₂O_5.3 epitaxial films using a strong oxidizing agent NaClO. The x value can be varied in a wide range of 5.3–6.0, maintaining the A-site cation-ordered perovskite structure, by changing the pH and temperature of NaClO. The single crystalline film with x = 6 exhibits large tetragonal distortion (c/a = 0.968) because of the small ionic radius of Y³⁺ and substrate-induced tensile strain. Unlike antiferromagnetic insulating YBaCo₂O_5.5, the fully oxidized film with x = 6 exhibits in-plane ferromagnetism and metallicity with a Curie temperature of 130 K possibly because of the double-exchange interaction between Co³⁺ and Co⁴⁺. Moreover, the YBaCo₂O₆ film exhibits huge magnetic anisotropy with a magnetic anisotropy constant of 1.5 × 10⁸ erg cm⁻³, demonstrating that the A-site cation-ordered perovskite structure is promising for obtaining high magnetocrystalline anisotropic materials.

中文翻译：

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通过湿化学全能氧化法制备的 A位置有序钙钛矿YBaCo ₂ O ₆外延薄膜中具有强磁晶各向异性的铁磁性†

由于Co轨道的大四方形畸变，A位阳离子排序的钙钛矿型钴矿RBaCo ₂ O _x（R =稀土元素）表现出令人着迷的物理特性，例如自旋态有序性和高氧导率。然而，扭曲的配位几何形状倾向于氧空位，导致难以获得化学计量相（x＝ 6）。例如，X在YBaCo ₂ ö _X，这在很大程度上是因为扭曲Y的小尺寸的共同轨道³⁺，迄今被限制在5.52。为了扩大x的可用范围，在这项研究中，我们进行了YBaCo的低温全位氧化_5.3外延膜中使用₂ O _5.3的强氧化剂NaClO。的X值可在宽范围的5.3-6.0变化，维持A位阳离子有序钙钛矿结构中，通过改变次氯酸钠的pH和温度。x = 6的单晶膜由于Y ³⁺的小离子半径和基体诱导的拉伸应变而表现出较大的四方畸变（ c / a = 0.968）。不同于反铁磁绝缘YBaCo ₂ O _5.5，具有x的完全氧化膜= 6表现出居里温度为130 K的面内铁磁性和金属性，可能是由于Co ³⁺和Co ⁴⁺之间的双重交换相互作用。此外，YBaCo ₂ O ₆膜表现出巨大的磁各向异性，其磁各向异性常数为1.5×10 ⁸ erg cm ^-3，表明A位阳离子序的钙钛矿结构有望获得高磁晶各向异性材料。