标题： 绝热去磁制冷与反铁磁有序的NaGdP$_2$O$_7$ 显示英文标题

标题： Adiabatic demagnetization refrigeration with antiferromagnetically ordered NaGdP$_2$O$_7$

摘要： 我们对NaGdP$_2$O$_7$的结构、磁性和热力学性质以及绝热去磁制冷（ADR）性能进行了全面研究。 尽管NaGdP$_2$O$_7$在零场下在Néel温度$T_{\rm N} = 570$mK时表现出反铁磁有序，但在施加$\mu_0H = 5$T的磁场下，从$T = 2$K开始的ADR实验达到了最低温度220 mK。升温回到$T = 2$K所需的时间超过60小时，大约是其基于Yb的类似物的50倍，这突显了NaGdP$_2$O$_7$在双级ADR系统中作为高效预冷阶段的潜力。 我们证明NaGdP$_2$O$_7$可以看作是具有反铁磁链间耦合的铁磁自旋链网络，并且还研究了反铁磁有序对磁熵的影响。 我们发现，在磁有序状态下，熵的温度依赖性比其磁场依赖性起着更主要的作用。 显示英文摘要

摘要： We present a comprehensive study of the structural, magnetic, and thermodynamic properties, as well as the adiabatic demagnetization refrigeration (ADR) performance of NaGdP$_2$O$_7$. Although NaGdP$_2$O$_7$ exhibits antiferromagnetic ordering at a N\'eel temperature of $T_{\rm N} = 570$ mK in zero field, ADR experiments achieved a minimum temperature of 220 mK starting from $T = 2$ K under an applied magnetic field of $\mu_0H = 5$ T. The warm-up time back to $T = 2$ K exceeds 60 hours, which is roughly 50 times longer than that of its Yb-based analogue, underscoring the potential of NaGdP$_2$O$_7$ as an efficient precooling stage in double-stage ADR systems. We show that NaGdP$_2$O$_7$ can be seen as a network of ferromagnetic spin chains with antiferromagnetic interchain couplings and also investigate the influence of antiferromagnetic ordering on the magnetic entropy. We find that the temperature dependence of the entropy plays a more dominant role than its magnetic field dependence in the magnetically ordered state.