Abstract Future advancements in magnetocaloric refrigeration/heat pumping technologies depend on the discovery of new materials that demonstrate large, tunable magnetocaloric effects (MCEs) in the vicinity of coupled magnetic and structural phase transitions that occur reversibly with minimum hysteresis. With this in mind, we investigate phase transitions, microstructure, magnetic, thermal, magnetocaloric, and transport properties of (Gd5-xScx)Si1.8Ge2.2 compounds. Replacement of magnetic Gd with non-magnetic Sc in Gd5-xScxSi1.8Ge2.2 increases the ferromagnetic to paramagnetic first order phase transition temperature, TC, with only a minor reduction in MCE when x ≤ 0.2. We also demonstrate that hydrostatic pressure further increases TC and reduces the hysteresis of the first order phase transition in Gd4.8Sc0.2Si1.8Ge2.2 from 7 to 4 K. Temperature-dependent x-ray powder diffraction study of Gd4.8Sc0.2Si1.8Ge2.2 confirms the monoclinic ↔ orthorhombic structural transformation at TC, in agreement with magnetic, calorimetric, and electrical transport measurements. In addition to the substantial magnetocaloric effect, a large magnetoresistance of ∼20% is also observed in Gd4.8Sc0.2Si1.8Ge2.2 for ΔH = 50 kOe in the vicinity of the magnetostructural transition. In a drastic reversal of the initial doping behavior further additions of Sc (x > 0.2) suppress formation of the monoclinic phase, change the nature of the transition from first-to second-order, and reduce both the transition temperature and magnetocaloric effect.

中文翻译：

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(Gd 5-x Sc x )Si 1.8 Ge 2.2 中的磁结构相变和磁热效应

摘要 磁热制冷/热泵技术的未来进步取决于新材料的发现，这些材料在磁耦合和结构相变附近表现出大的、可调谐的磁热效应 (MCE)，磁热和结构相变以最小的滞后可逆发生。考虑到这一点，我们研究了 (Gd5-xScx)Si1.8Ge2.2 化合物的相变、微观结构、磁性、热、磁热和传输特性。在 Gd5-xScxSi1.8Ge2.2 中用非磁性 Sc 替换磁性 Gd 会增加铁磁性到顺磁性的一级相变温度 TC，当 x ≤ 0.2 时，MCE 仅略有降低。我们还证明静水压力进一步增加了 TC 并降低了 Gd4.8Sc0.2Si1.8Ge2.2 中一级相变的滞后从 7 到 4 K。Gd4.8Sc0.2Si1.8Ge2.2 的温度相关 X 射线粉末衍射研究证实了 TC 处的单斜↔ 正交结构转变，与磁、量热和电传输测量一致。除了显着的磁热效应之外，在磁结构转变附近对于 ΔH = 50 kOe 在 Gd4.8Sc0.2Si1.8Ge2.2 中也观察到了大约 20% 的大磁阻。在初始掺杂行为的急剧逆转中，进一步添加 Sc (x > 0.2) 抑制了单斜晶相的形成，改变了从一级到二级转变的性质，并降低了转变温度和磁热效应。量热和电传输测量。除了显着的磁热效应之外，在磁结构转变附近对于 ΔH = 50 kOe 在 Gd4.8Sc0.2Si1.8Ge2.2 中也观察到了大约 20% 的大磁阻。在初始掺杂行为的急剧逆转中，进一步添加 Sc (x > 0.2) 抑制了单斜晶相的形成，改变了从一级到二级转变的性质，并降低了转变温度和磁热效应。量热和电传输测量。除了显着的磁热效应之外，在磁结构转变附近对于 ΔH = 50 kOe 在 Gd4.8Sc0.2Si1.8Ge2.2 中也观察到了大约 20% 的大磁阻。在初始掺杂行为的急剧逆转中，进一步添加 Sc (x > 0.2) 抑制了单斜相的形成，改变了从一级到二级转变的性质，并降低了转变温度和磁热效应。