Wu Haoyu, Fang Zhilin, Jiang Pengfei, Yang Tao
College of Chemistry and Chemical Engineering, Chongqing University, Chongqing 401331, China.
Dalton Trans. 2024 Mar 19;53(12):5382-5390. doi: 10.1039/d3dt04016j.
In this work, we report the structural and magnetic characterization of two new B-site rock-salt ordered double perovskites ALaCoTeO (A = K and Na) with mixed A-site cations. KLaCoTeO crystallizes in the space group 4/ with a long-range ordering degree of 84.8% for the A-site K/La cations, whereas NaLaCoTeO adopts an unexpected triclinically distorted 1̄-structure with Na/La disordering, validated by combined Rietveld refinements against high-resolution neutron diffraction data and Cu K X-ray powder diffraction data. Magnetic susceptibility at low temperatures shows clear antiferromagnetic (AFM) transitions for both compounds. KLaCoTeO exhibits the highest AFM transition temperature of 20 K amongst all the Co/Te-ordered 3C-type ACoTeO (A = Pb, Sr, and Ca) and ALaCoTeO double perovskites due to its larger Co-O-Te bond angle and A-site cationic ordering-induced larger distortion of the Co-based face-centered cubic sublattice. Moreover, we found that the average radius of the A-site cations plays a decisive role in the AFM transition temperatures of all these ordered double perovskites, that is, a larger A-site cation always results in a higher AFM transition temperature. This provides a strategy to subtly manipulate the magnetic properties of ordered double perovskites.
在本工作中，我们报道了两种具有混合A位阳离子的新型B位岩盐有序双钙钛矿ALaCoTeO（A = K和Na）的结构和磁性表征。KLaCoTeO在空间群4/中结晶，A位K/La阳离子的长程有序度为84.8%，而NaLaCoTeO采用了意想不到的三斜畸变1̄结构，存在Na/La无序，这通过对高分辨率中子衍射数据和Cu K X射线粉末衍射数据进行联合Rietveld精修得到验证。低温下的磁化率表明这两种化合物都有明显的反铁磁（AFM）转变。在所有Co/Te有序的3C型ACoTeO（A = Pb、Sr和Ca）和ALaCoTeO双钙钛矿中，KLaCoTeO由于其较大的Co-O-Te键角以及A位阳离子有序诱导的基于Co的面心立方亚晶格的更大畸变，表现出最高的AFM转变温度20K。此外，我们发现A位阳离子的平均半径在所有这些有序双钙钛矿的AFM转变温度中起决定性作用，即较大的A位阳离子总是导致更高的AFM转变温度。这提供了一种巧妙调控有序双钙钛矿磁性的策略。
