Intermetallics ( IF 4.4 ) Pub Date : 2021-07-29 , DOI: 10.1016/j.intermet.2021.107297 Subarna Datta 1 , Shovan Dan 2 , Shuvankar Gupta 1 , Sudip Chakraborty 1 , Chandan Mazumdar 1
The detailed X-ray diffraction studies of the structural phase along with its thermal expansion properties have been carried out of the rare-earth based compounds Nd2Fe17-xCrx (x = 0, 0.5, 1.0, and 2.0). They are crystallized in the rhombohedral structure (Th2Zn17 type) with space group R-3m. A very negligible (close to zero) thermal expansion coefficient |α| = 1.9 × 10−6 K−1, was found over a large temperature range 15–320 K in Nd2Fe16.5Cr0.5 compound (TC ~ 366 K) attributable to the diminution of magneto-volume effect. This kind of zero thermal expansion (ZTE) magnetic system has a great practical significance having TC higher than 300 K. The parent compound Nd2Fe17, as a magnetocaloric material, has high relative cooling power (RCP) (625 J kg−1 at μ0H = 0–9 T), elevated operational temperature (326 K) and comparatively high entropy change (|ΔSM|max) at TC. Because of these properties Nd2Fe17 can operate as a promising refrigerating system. The critical behaviour of all the four samples is studied by means of the isotherm magnetization in the vicinity of TC. The critical exponents are evaluated using various methods, for instance, modified Arrott plot, critical isotherm, Kouvel–Fisher plot in addition to the study of magnetocaloric effect. From the critical analysis it is revealed that all the four samples belong to different types of universal magnetic class.
中文翻译:
Cr取代铁磁Nd2Fe17的多功能特性
已经对稀土基化合物 Nd 2 Fe 17- x Cr x ( x = 0、0.5、1.0和 2.0)进行了结构相及其热膨胀特性的详细 X 射线衍射研究。它们以菱形结构(Th 2 Zn 17型)结晶,空间群为R-3m。一个可以忽略不计(接近于零)的热膨胀系数 | α | = 1.9 × 10 -6 K -1,在 Nd 2 Fe 16.5 Cr 0.5化合物(T C ~ 366 K)归因于磁体积效应的减弱。这种零热膨胀(ZTE)磁系统具有很大的实际意义,其T C高于300 K。母体化合物Nd 2 Fe 17作为磁热材料,具有较高的相对冷却能力(RCP)(625 J kg - 1 at μ 0 H = 0–9 T),升高的操作温度 (326 K) 和相对较高的熵变 (|Δ S M | max ) 在T C。由于这些特性 Nd 2 Fe 17可以作为一个有前途的制冷系统运行。通过T C附近的等温磁化强度研究所有四个样品的临界行为。除了研究磁热效应外,还使用各种方法评估临界指数,例如修正的阿罗特图、临界等温线、Kouvel-Fisher 图。从批判性分析中可以看出,所有四个样本都属于不同类型的通用磁类。