Cho Keunki, Shon Wonhyuk, Bae Jaehan, Lee Jaewoong, Yoon Seungha, Kim Jinhee, Rhyee Jong-Soo, Cho Beongki
School of Materials Science and Engineering, Gwangju Institute of Science and Technology, Gwangju 61005, Republic of Korea.
Green Energy and Nano Technology R&D Group, Korea Institute of Industrial Technology, Gwangju 61012, Republic of Korea.
Materials (Basel). 2023 Mar 30;16(7):2771. doi: 10.3390/ma16072771.
Magnetic anisotropy strongly influences the performance of the magnetocaloric effect. We investigated the magnetocaloric properties of the NdAlGe single crystal with I4md structure. The temperature-dependent magnetization revealed significant anisotropic properties; stable antiferromagnetic transition at = 6 K for //a and meta-magnetic spin reorientation at low temperature ( ≤ 5 K) within an intermediate field ( = 2 T) for //c. During the metamagnetic spin reorientation, the abrupt change of the magnetic entropy leads to a significant magnetocaloric effect with negative magnetic entropy change (∆) by -13.80 J kg K at = 5.5 K for = 5 T along the H//c axis. In addition, the antiferromagnetic state for H//a shows the inverse magnetocaloric effect(I-MCE) by positive entropy change ∆ = 2.64 J kg K at = 6 K for = 5 T. This giant MCE accompanied by the metamagnetic transition resulted in a significantly large relative cooling power (158 J/kg at = 5 T) for //c. The giant MCE and I-MCE can be applied to the rotational magnetocaloric effect (R-MCE) depending on the crystal orientations. NdAlGe exhibits rotational entropy change ∆ = -12.85 J kg K at = 7.5 K, = 5 T. With comparison to conventional MCE materials, NdAlGe is suggested as promising candidate of R-MCE, which is a novel type of magnetic refrigeration system.
磁各向异性强烈影响磁热效应的性能。我们研究了具有I4md结构的NdAlGe单晶的磁热性能。随温度变化的磁化强度显示出显著的各向异性特性；对于//a，在6 K时存在稳定的反铁磁转变；对于//c，在低温（≤5 K）且处于中间场（= 2 T）时存在亚磁自旋重取向。在亚磁自旋重取向过程中，磁熵的突然变化导致了显著的磁热效应，沿H//c轴在5 T、5.5 K时磁熵变化（∆）为 -13.80 J kg⁻¹ K⁻¹ 。此外，对于H//a的反铁磁态，在5 T、6 K时通过正熵变∆ = 2.64 J kg⁻¹ K⁻¹ 显示出逆磁热效应（I-MCE）。这种伴随着亚磁转变的巨大磁热效应导致对于//c在5 T时具有显著大的相对制冷量（158 J/kg）。取决于晶体取向，巨大磁热效应和逆磁热效应可应用于旋转磁热效应（R-MCE）。NdAlGe在7.5 K、5 T时表现出旋转熵变∆ = -12.85 J kg⁻¹ K⁻¹ 。与传统磁热效应材料相比，NdAlGe被认为是旋转磁热效应（一种新型磁制冷系统）的有前途的候选材料。
