Pramanik P, Singha A D, Reehuis M, Pittala S, Joshi D C, Sarkar T, Tovar M, Hoser A, Hoffmann J-U, Thota S
Department of Physics, Indian Institute of Technology Guwahati, Guwahati, Assam 781039, India.
Department of Materials Science and Engineering, Uppsala University, SE-751 21 Uppsala, Sweden.
J Phys Condens Matter. 2024 May 31;36(35). doi: 10.1088/1361-648X/ad4adc.
Local magnetostructural changes and dynamical spin fluctuations in doubly diluted spinel TiMn(FeCo)Ohas been reported by means of neutron diffraction and magnetization studies. Two distinct sets of compositions (i)(Ti) = 0.20 and(Fe) = 0.18; (ii)(Ti) = 0.40 and(Fe) = 0.435 have been considered for this study. The first compound of equivalent stoichiometry TiMnFeCoOexhibits enhanced tetragonal distortion across the ferrimagnetic transition temperature= 258 K in comparison to the end compound MnCoO(∼ 180 K) with a characteristic ratio/√2of 0.99795(8) demonstrating robust lattice-spin-orbital coupling. However, in the second case TiMnFeCoOwith higher-site compositions, the presence of Jahn-Teller ions with distinct behavior appears to counterbalance the strong tetragonal distortion thereby ceasing the lattice-spin-orbital coupling. Both the investigated systems show the coexistence of noncollinear antiferromagnetic and ferrimagnetic components in cubic and tetragonal settings. On the other hand, the dynamical ac-susceptibility,() reveals a cluster spin-glass state with Gabay-Toulouse (GT) like mixed phases behaviour below. Such dispersive behaviour appears to be sensitive to the level of octahedral substitution. Further, the field dependence of() follows the weak anisotropic GT-line behaviour with crossover exponent Φ lies in the range 1.38-1.52 on the-plane which is in contrast to the-site Ti substituted MnCoOspinel that appears to follow irreversible non-mean-field AT-line behaviour (Φ ∼ 3 +). Finally, the Arrott plots analysis indicates the presence of a pseudo first-order like transition (< 20 K) which is in consonance with and zero crossover of the magnetic entropy change within the frozen spin-glass regime.
通过中子衍射和磁化研究报道了双稀释尖晶石TiMn(FeCo)O中的局部磁结构变化和动态自旋涨落。本研究考虑了两组不同的成分：(i)(Ti)=0.20且(Fe)=0.18；(ii)(Ti)=0.40且(Fe)=0.435。与端化合物MnCoO（~180 K）相比，化学计量比等效的第一种化合物TiMnFeCoO在亚铁磁转变温度 = 258 K时表现出增强的四方畸变，其特征比 /√2 为0.99795(8)，表明存在强大的晶格 - 自旋 - 轨道耦合。然而，在第二种具有更高位点组成的TiMnFeCoO情况下，具有不同行为的 Jahn - Teller 离子的存在似乎抵消了强烈的四方畸变，从而终止了晶格 - 自旋 - 轨道耦合。所研究的两个系统在立方和四方结构中均显示出非共线反铁磁和亚铁磁成分的共存。另一方面，动态交流磁化率 () 在低于 时揭示了具有类似Gabay - Toulouse（GT）混合相行为的团簇自旋玻璃态。这种色散行为似乎对八面体取代水平敏感。此外，() 的场依赖性遵循弱各向异性的GT线行为，在平面上的交叉指数Φ在1.38 - 1.52范围内，这与位点Ti取代的MnCoO尖晶石形成对比，后者似乎遵循不可逆的非平均场AT线行为（Φ ~ 3 +）。最后，Arrott图分析表明存在类似准一级的转变（< 20 K），这与冻结自旋玻璃态内磁熵变化的 和零交叉一致。
