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_0.95Co_0.75Cu_0.25Ge. 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.

中文翻译：

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Mn-空位化合物Mn 0.95 Co 0.75 Cu 0.25 Ge中的连续反磁和正磁热效应

在基于MnCoGe的材料中，铁磁-结构转变已得到广泛研究。然而，很少有文献报道从反铁磁（AFM）正交相到铁磁（FM）六方相的磁结构转变（MST），这可能导致较大的逆磁热效应（MCE）。在此，Mn空位的引入降低了结构转变温度，同时在正交相中保持了AFM状态，从而成功实现了Mn _0.95 Co _0.75 Cu _0.25中的AFM-FM MST。哥 此外，分别在第一阶AFM-FM MST和第二阶FM-顺磁（PM）跃迁附近观察到了连续的逆MCE和正常MCE。基于此特殊功能，提出了一种恒温器，该恒温器可以通过简单地施加相同的磁化/退磁循环来释放高于临界温度的热量，同时吸收低于临界温度的热量。该恒温器在许多需要恒定温度的应用中非常有用，例如低温恒温器和恒温箱。