It has been known that a LaCaMnO (LMO) bulk sample has the maximum magnetic entropy change (|Δ|) larger than |Δ| of Gd – a conventional magnetocaloric (MC) material. However, such large change just takes place in a narrow range of temperature because of its first-order character. This influences the working temperature range (Δ) and relative cooling power () of LMO. Previous works have revealed that the fabrication of LMO nanoparticles with the second-order character would improve the magnitude of Δ and , and reduce magnetic hysteresis losses. In this work, we suggest that the combination of LMO nanoparticles (NPs) with Gd powder as nanocomposites (NCPs), termed (100-)LMO + Gd with = 50 and 75 wt%, further enhances Δ from 60 to ∼94 K (in the range = 220–314 K) for applied fields = 5–20 kOe. These values are larger than those of initial materials Gd and LMO NPs (Δ ≈ 40 K), reported composites (Δ < 50 K), and even the composites fabricated from a LMO bulk and Gd powder (Δ < 60 K) in the same fields. Additionally, all NCPs exhibit the second-order character, and of optimal NCPs is nearly comparable to that of Gd. These features demonstrate application potentials of NCPs for conventional refrigerators operating in a large temperature range.

中文翻译：

---

La2/3Ca1/3MnO3/Gd 纳米复合材料在大温度范围内增强的磁热响应

已知 LaCaMnO (LMO) 块状样品的最大磁熵变 (|Δ|) 大于 |Δ| Gd——一种传统的磁热（MC）材料。然而，由于其一阶特性，如此大的变化只发生在很窄的温度范围内。这会影响 LMO 的工作温度范围 (Δ) 和相对冷却功率 ()。之前的工作表明，制造具有二阶特性的 LMO 纳米粒子可以提高 Δ 和 的大小，并减少磁滞损耗。在这项工作中，我们建议将 LMO 纳米颗粒 (NP) 与 Gd 粉末组合作为纳米复合材料 (NCP)，称为 (100-)LMO + Gd，其中 = 50 和 75 wt%，进一步将 Δ 从 60 K 提高到~94 K（范围 = 220–314 K)，应用场 = 5–20 kOe。这些值大于初始材料 Gd 和 LMO 纳米颗粒 (Δ ≈ 40 K)、报道的复合材料 (Δ < 50 K)，甚至比在相同条件下由 LMO 块体和 Gd 粉末制成的复合材料 (Δ < 60 K) 的值更大。字段。此外，所有 NCP 均表现出二阶特性，并且最佳 NCP 的性能几乎与 Gd 相当。这些特性展示了 NCP 在大温度范围内运行的传统冰箱的应用潜力。