Abstract Gd-based metallic glasses enable a wider exploration for excellent magnetocaloric materials due to no requirement of compositional stoichiometry, but these metallic glasses generally show a lower ordering temperature compared with corresponding intermetallic compounds. In this paper, critical behaviors for magnetic transitions in both Gd6Co4.85 intermetallic compound and metallic glass were carefully studied based on isothermal magnetization to reveal the exchange interactions in these two different structural stages, together with experimental electronic density analyses on the compound. Obtained critical exponents close to the theoretical values predicted by the mean-field theory (MFT) in both structures suggest the majority of Gd–Gd long-range exchange interactions, while the Co-Co direct interaction accounts for the deviation of these exponents from the theoretical values in MFT. This is likely a common feature for rare earth – transition metal ferrimagnets. The ordered Co atoms in the intermetallic compound exhibit a high-spin state (~4.6 μB), in contrast with the low-spin state of Co (~1.2 μB) in the metallic glass. The reduced spin is associated with the liquid-like structure in the metallic glass (e.g. longer Co-Co distances) and responsible for the low ordering temperature. This work also indicates that the substitution of p-block elements like Al prefers the site to diminish Co moments, leading to the significantly reduced ordering temperature, and thus emphasizes the critical role of d-electron elements to maintain enough direct exchange interactions for proper transition temperature in the development of new metallic glasses with giant magnetocaloric effects.

中文翻译：

---

金属玻璃中直接交换耦合的抑制：Gd6Co4.85 金属间化合物和金属玻璃中临界和电子行为的比较研究

摘要 钆基金属玻璃由于不要求组成化学计量比，因此可以更广泛地探索优异的磁热材料，但与相应的金属间化合物相比，这些金属玻璃通常表现出较低的有序温度。在本文中，基于等温磁化强度仔细研究了 Gd6Co4.85 金属间化合物和金属玻璃中磁转变的临界行为，以揭示这两个不同结构阶段的交换相互作用，以及对化合物的实验电子密度分析。在两种结构中获得的接近平均场理论（MFT）预测的理论值的临界指数表明大部分 Gd-Gd 长程交换相互作用，而 Co-Co 直接相互作用解释了这些指数与 MFT 理论值的偏差。这可能是稀土过渡金属亚铁磁体的共同特征。金属间化合物中有序的 Co 原子表现出高自旋态（~4.6 μB），而金属玻璃中的 Co 原子呈低自旋态（~1.2 μB）。减少的自旋与金属玻璃中的液体状结构有关（例如更长的 Co-Co 距离），并导致低有序温度。这项工作还表明，像 Al 等 p 区元素的取代更喜欢该位点来减少 Co 矩，导致排序温度显着降低，