The criticality-enhanced magnetocaloric effect (MCE) near a field-induced quantum critical point (QCP) in the spin systems constitutes a very promising and highly tunable alternative to conventional adiabatic demagnetization refrigeration. Strong fluctuations in the low-$T$ quantum critical regime can give rise to a large thermal entropy change and thus significant cooling effect when approaching the QCP. In this work, through efficient and accurate many-body calculations, we show there exists a significant inverse MCE(iMCE) in the spin-1 quantum chain materials(CH$_3$)$_4$NNi(NO$_2$)$_3$ (TMNIN) and NiCl$_2$-4SC(NH$_2$)$_2$ (DTN), where DTN has substantial low-$T$ refrigeration capacity while requiring only moderate magnetic fields. The iMCE characteristics, including the adiabatic temperature change $ΔT_{\rm ad}$, isothermal entropy change $ΔS$, differential Grüneisen parameter, and the entropy change rate, are obtained with quantum many-body calculations at finite temperature. The cooling performance, i.e., the efficiency factor and hold time, of the two compounds is also discussed. Based on the many-body calculations on realistic models for the spin-chain materials, we conclude that the compound DTN constitutes a very promising and highly efficient quantum magnetic coolant with pronounced iMCE properties. We advocate that such quantum magnets can be used in cryofree refrigeration for space applications and quantum computing environments.
Frustration induced inversion of magnetocaloric effect and enhanced cooling power in substituted Pyrochlore Iridates
我们研究了局部3d Cr 3+磁矩部分取代5d Ir 4+位置对Y2 Ir 2 O 7（YIO）烧绿石铱酸盐磁热性能的影响。我们发现，Y2 Ir 2-xCrxO 7（YICO）发生团簇玻璃化转变，可能是由于RKKY一样的本地化的Cr 3+时刻占据烧绿石网络中的随机站点之间的相互作用，介导的5d Ir传导电子。铁磁团簇和反铁磁团簇的共存导致了常规磁热效应和逆磁热效应。我们观察到显着增强传统以及逆MCE与替代。虽然传统的MCE和反MCE在取代的铱酸盐的值不大，效果跨越一个巨大的工作温度窗口，从而导致数量级的增强冷却功率，该值是可比的标准磁热材料。
High-resolution alternating-field technique to determine the magnetocaloric effect of metals down to very low temperatures
磁热效应或“磁格吕奈森比”$Γ_H=T^{-1}(dT/dH)_S$量化了当在绝热条件下改变所施加的磁场时材料的冷却或加热。最近，这一性质在量子临界性领域引起了相当大的兴趣。在这里，我们报告的低频交变场技术的发展，它允许进行连续的温度扫描的$Γ_H(T)$小单晶非常高的精度和非常低的温度。对掺杂YbRh $_2$ Si $_2$的测量表明，用这种方法可以比用磁化强度和比热计算更快、更准确地确定$Γ_H(T)$。
Magnetic phase diagram, magnetotransport and inverse magnetocaloric effect in the noncollinear antiferromagnet Mn$_5$Si$_3$
反铁磁体Mn $_5$ Si $_3$最近引起了人们的注意，因为非共线自旋排列已被证明产生拓扑异常霍尔效应和逆磁热效应。在这里，我们使用助熔剂生长法合成Mn $_5$ Si $_3$单晶。我们通过磁化确定了相图，并测量了磁阻和霍尔效应。我们发现在低温下的共线和非共线的反铁磁相，此外，第三个磁性相，在两个反铁磁相之间，具有铁磁特性。后者的磁性相可能是由铜夹杂物产生的应变，导致淬灭的混合字符在此化合物中的磁有序的波动。
Magnetic and magnetotransport behavior of RFe5Al7 (R= Gd and Dy): Observation of re-entrant inverse-magnetocaloric phenomenon and asymmetric magnetoresistance behavior
Direct measurements of the magnetocaloric effect in ribbon samples of Heusler alloys Ni - Mn - M (M = In, Sn)
直接测量的磁热效应在快速淬火薄带的Mn 50 Ni 40 In 10和Ni 50 Mn 37 Sn 13 Heusler合金，在磁制冷技术的潜在应用，样品进行。测量是通过一种精确的方法进行的，该方法是基于测量样品在受到调制磁场的同时温度的振荡幅度。在所研究的成分中，发现了与磁性（顺磁体-铁磁体-反铁磁体）和结构（奥氏体-马氏体）相变相关的正磁热效应和逆磁热效应，在铁磁相变附近还观察到了小值的逆磁热效应。
Magnetic and magnetocaloric properties of quasi-one-dimensional Ising spin chain CoV$_{2}$O$_{6}$
通过磁化强度和热容测量研究了反铁磁Ising自旋链CoV $_{2}$ O $_{6}$的磁性和磁热性质.单斜晶系的$α$ $_{2}$ O $_{6}$和三斜晶系的$γ$ $_{2}$ O $_{6}$都表现出通过具有1/3磁化平台的中间亚铁磁态从反铁磁态到铁磁态的场诱导变磁转变.由于这种场致变磁转变，这些系统显示出大的常规以及逆磁热效应。在$α$ $_{2}$ O $_{6}$中，当沿$c$轴施加磁场时，我们观察到低温下场诱导的复杂磁相和多个磁化平台。从磁化强度、磁熵变和热容的温度和场依赖性确定了几个临界温度和场，构建了$H$ - $T$相图。与$α$ $_{2}$ O $_{6}$相比，$γ$ $_{2}$ O $_{6}$显示出相对简单的磁相图.由于在低或中等外加磁场下具有大的磁熵变和绝热温度变化，$γ$ -CoV $_{2}$ O $_{6}$可以被认为是低温区的磁制冷剂。
Realization of large magnetocaloric effect in the Kagome antiferromagnet Gd3BWO9 for Sub-Kelvin cryogenic refrigeration
Wuhan National High Magnetic Field Center and School of Physics, Huazhong University of Science and Technology（华中科技大学物理学院）；Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences（中国科学院物理研究所）；Anhui Key Laboratory of Low-energy Quantum Materials and Devices, High Magnetic Field Laboratory, Chinese Academy of Sciences（中国科学院强磁场科学中心）；School of Fundamental Physical quantum Physics, Huazhong University of Science and Technology（华中科技大学前沿物理量子科学学院）
Spin-Chain Incipient Magnetocaloric Effect and Rare-Earth Controlled Switching in the Haldane-Chain System, R2BaNiO5
Rajiv Gandhi Institute of Petroleum Technology（拉吉夫·甘地石油技术学院）；Department of Physics, Dr. B. R. Ambedkar National Institute of Technology（德里·B·R·安贝德卡尔国家理工学院物理系）
Finite-temperature quantum Monte Carlo study of Dirac quantum criticality: Algorithmic advances and comprehensive analysis
Institute of Modern Physics, Northwest University（西北大学现代物理研究所）；Hefei National Laboratory（合肥国家实验室）；School of Physics, Northwest University（西北大学物理学院）；Shaanxi Key Laboratory for Theoretical Physics Frontiers（陕西理论物理前沿重点实验室）；Fundamental Discipline Research Center for Quantum Science and Technology of Shaanxi Province（陕西省量子科学与技术基础学科研究中心）
