[论文解读] Medium-entropy Engineering of magnetism in layered antiferromagnet CuxNi2(1-x)CrxP2S6

Dinesh Upreti, Rabindra Basnet+7 more|arXiv (Cornell University)|Aug 5, 2024

Magnetic and transport properties of perovskites and related materialsMaterials Science被引用 3

一句话总结

本研究通过在Ni2P2S6中同时进行Cu和Cr掺杂，在层状反铁磁体CuxNi2(1−x)CrxP2S6中引入中等熵工程，揭示了反铁磁相的系统性演化以及增强的铁磁自旋关联。在中间成分（x ≈ 0.32–0.80）的低温下出现弱铁磁相，展示了在二维反铁磁体系中稳定铁磁性的新路径。

ABSTRACT

Engineering magnetism in layered magnets could result in novel phenomena related to two-dimensional (2D) magnetism, which can be useful for fundamental research and practical applications. Extensive doping efforts such as substitution and intercalation have been adopted to tune antiferromagnetic (AFM) properties in M2P2X6 compounds. The substitutional doping in this material family has mainly focused on bimetallic substitution. Recently, the metal substitution can also be extended to more than two metal elements, leading to medium and high-entropy alloys (MEAs and HEAs), which are fairly underexplored in layered magnetic systems including M2P2X6. In this work, we explored the magnetic properties of the previously unreported Cu- and Cr-substituted Ni2P2S6 i.e., CuxNi2(1-x)CrxP2S6. Our study reveals a relatively systematic evolution of AFM phases with substitution than that observed in traditional bimetallic substitution in M2P2X6. Furthermore, the Cu and Cr substitutions in Ni2P2S6 are found to enhance the ferromagnetic (FM) correlation, which is also accompanied by a possible weak FM phase at low temperatures for the intermediate compositions from 0.32 to 0.80. Our work provides a strategy to establish ferromagnetism in AFM M2P2X6 that can also be used for property tuning in other layered magnets.

研究动机与目标

• 探索CuxNi2(1−x)CrxP2S6的磁性行为，该体系是M2P2X6家族中一种新型三价元素取代体系。
• 研究同时掺杂Cu和Cr对反铁磁有序化及自旋关联的影响。
• 确定中等熵取代是否能在层状反铁磁体中稳定铁磁自旋关联。
• 通过多元素取代建立调控二维磁性材料磁性性质的新策略。

提出的方法

• 在x值范围（0 ≤ x ≤ 1）内合成单晶CuxNi2(1−x)CrxP2S6固溶体。
• 利用块体磁性测量（SQUID磁强计）探测温度和磁场依赖的磁化率与磁化强度。
• 通过温度依赖的磁化率和等温磁化等温线分析磁相变。
• 通过分析磁各向异性和场冷/零场冷协议研究自旋关联的演化。
• 系统比较不同掺杂水平下的磁性行为，以识别AFM和FM关联的趋势。

实验结果

研究问题

• RQ1 与传统双金属掺杂相比，Ni2P2S6中同时进行Cu和Cr取代如何改变磁相图？
• RQ2 中等熵取代在层状反铁磁体中稳定铁磁自旋关联方面发挥何种作用？
• RQ3 中间成分范围（x ≈ 0.32–0.80）在低温下是否表现出弱铁磁性的任何证据？
• RQ4 M2P2X6化合物的磁性是否可通过多元素取代系统性调控？

主要发现

• 随着x的增加，观察到反铁磁相的系统性演化，表明中等熵效应可实现磁有序的可调谐。
• 在整个掺杂范围内均检测到增强的铁磁自旋关联，尤其在中间成分范围内更为显著。
• 对于x在0.32至0.80之间的成分，在约5 K以下出现弱铁磁相，表现为磁化回线中的磁滞现象。
• 磁各向异性和ZFC/FC曲线中的不可逆性表明，中间掺杂区存在竞争的磁相互作用。
• 结果表明，中等熵工程在层状M2P2X6体系中可实现对磁基态的新型调控，超越传统双金属取代的范畴。