Successive inverse and normal magnetocaloric effects in the Mn-vacancy compound Mn0.95Co0.75Cu0.25Ge

Abstract

Ferromagnetic-structural transformation has been studied widely in MnCoGe-based materials. However, the magnetostructural transition (MST) from antiferromagnetic (AFM) orthorhombic phase to ferromagnetic (FM) hexagonal phase, which may lead to a large inverse magnetocaloric effect (MCE), has rarely been reported. Here, the introduction of Mn vacancy lowers the structural transition temperature while retains the AFM state in the orthorhombic phase, thus successfully realizing the AFM-FM MST in Mn 0.95 Co 0.75 Cu 0.25 Ge. Moreover, successive inverse and normal MCEs are observed around the first-order AFM-FM MST and the second-order FM-paramagnetic (PM) transition, respectively. A thermostat is proposed based on this special feature, which could release heat above the critical temperature while absorb heat below the critical temperature by simply applying the same magnetization/demagnetization cycles. This thermostat can be very useful in many applications where a constant temperature is required, such as cryostats and incubators. magnetocaloric, magnetically ordered materials, phase transitions

Effect of doping with rare-earth element La in MnCoGe system

“…元素化学替代: 元素替代法是最为常见、也是较容易 控制和调整相变温度的方法. 用Si [13] , Sn [14,15] , Al [16,17] , Fe [18,19] , Cr [20] , V [21] , Co [22] , Ti [23] , Cu [24][25][26] , Ni [27,28] , Zn [29] , Ga [30] , In [12] , Si [31] , Zr和Pd [32] 等元素替代过渡金属(Mn, Co)或主族元素(Ge)都被证明是有效的. Liu等人 [33] [34] 及Fe-Ga磁致伸缩材料 [35]…”

Microstructure and transition behavior of Fe<sub>2</sub>P-based first-order magnetic phase-transition alloys

“…为了避免剧毒元 素As的安全隐患, 研究者们先后尝试采用Ge [5,6] , Si [7,8] 等元素取代As, 成功开发出无毒、低成本和磁热性能 优异的(Mn, Fe) 2 (P, Si)合金. 然而, 与其他一级磁相变 合金一样 [9][10][11][12] , (Mn, Fe) 2 (P, Si)合金存在着热滞大、相 变可逆性差等问题, 限制了其在制冷循环中的制冷效 率. Guillou等人 [13] 研究发现, 在(Mn, Fe) 2 (P, Si)合金中 引入硼原子可以将热滞降低到1.6 K左右, 相变可逆性 Fe 2 P-based first-order magnetic phase-transition alloys have been considered as one of the best candidates for roomtemperature magnetic refrigeration applications due to their low cost, tunable working temperature range and superior magnetocaloric performance. Previous studies mainly focused on optimizing the magnetocaloric properties as well as uncovering the spin-lattice-electronic multi-coupling in the Fe 2 P-based alloys, while the structure and phase transition behavior at the micrometer scale have rarely been reported.…”

Characterization of caloric effects for magnetostructural transition materials: State-of-the-art and prospects

“…荷兰代尔夫特大学的Caron等 人 [21] 提出一种"循环"测量方法, 解决了一级相变滞后 带来的测量不准确的影响. 这一方法已被证实能准确 地评估具有大滞后的一级相变磁热材料, 并被广泛采 用 [22,23] .…”