Zhivulin Vladimir E, Trofimov Evgeniy A, Gudkova Svetlana A, Pashkeev Igor Yu, Punda Alexander Yu, Gavrilyak Maksim, Zaitseva Olga V, Taskaev Sergey V, Podgornov Fedor V, Darwish Moustafa A, Almessiere Munirah A, Slimani Yassine, Baykal Abdulhadi, Trukhanov Sergei V, Trukhanov Alex V, Vinnik Denis A
Laboratory of Single Crystal Growth, South Ural State University, 454080 Chelyabinsk, Russia.
Department of Technology of Electronics Materials, National University of Science and Technology MISiS, Leninsky Prospekt 4, 119049 Moscow, Russia.
Nanomaterials (Basel). 2021 Apr 15;11(4):1014. doi: 10.3390/nano11041014.
La-, Nd- and La/Nd-based polysubstituted high-entropy oxides (HEOs) were produced by solid-state reactions. Composition of the B-site was fixed for all samples (CrMnFeCoNi) with varying of A-site cation (La, Nd and LaNd). Nominal chemical composition of the HEOs correlates well with initial calculated stoichiometry. All produced samples are single phase with perovskite-like structure. Average particle size is critically dependent on chemical composition. Minimal average particle size (~400 nm) was observed for the La-based sample and maximal average particle size (5.8 μm) was observed for the Nd-based sample. The values of the configurational entropy of mixing for each sample were calculated. Electrical properties were investigated in the wide range of temperatures (150-450 K) and frequencies (10-10 Hz). Results are discussed in terms of the variable range hopping and the small polaron hopping mechanisms. Magnetic properties were analyzed from the temperature and field dependences of the specific magnetization. The frustrated state of the spin subsystem was observed, and it can be a result of the increasing entropy state. From the Zero-Field-Cooling and Field-Cooling regimes (ZFC-FC) curves, we determine the average and S maximum size of a ferromagnetic nanocluster in a paramagnetic matrix. The average size of a ferromagnetic cluster is ~100 nm (La-CMFCNO) and ~60 nm (LN-CMFCNO). The S maximum size is ~210 nm (La-CMFCNO) and ~205 nm (LN-CMFCNO). For Nd-CMFCNO, spin glass state (ferromagnetic cluster lower than 30 nm) was observed due to f-d exchange at low temperatures.
通过固态反应制备了基于镧（La）、钕（Nd）和镧/钕的多取代高熵氧化物（HEO）。所有样品的B位组成固定为（CrMnFeCoNi），A位阳离子（La、Nd和LaNd）有所变化。HEO的名义化学成分与初始计算的化学计量比相关性良好。所有制备的样品均为具有钙钛矿-like结构的单相。平均粒径严重依赖于化学成分。基于La的样品观察到最小平均粒径（约400nm），基于Nd的样品观察到最大平均粒径（5.8μm）。计算了每个样品的混合组态熵值。在很宽的温度范围（150 - 450K）和频率范围（10 - 10Hz）内研究了电学性质。根据可变范围跳跃和小极化子跳跃机制对结果进行了讨论。从比磁化强度的温度和磁场依赖性分析了磁性。观察到自旋子系统的受挫状态，这可能是熵态增加的结果。从零场冷却和场冷却（ZFC - FC）曲线中，我们确定了顺磁基质中铁磁纳米团簇的平均值和S最大尺寸。铁磁团簇的平均尺寸约为100nm（La - CMFCNO）和约60nm（LN - CMFCNO）。S最大尺寸约为210nm（La - CMFCNO）和约205nm（LN - CMFCNO）。对于Nd - CMFCNO，由于低温下的f - d交换，观察到自旋玻璃态（铁磁团簇低于30nm）。
