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首页> 外文期刊>The journal of physical chemistry, B. Condensed matter, materials, surfaces, interfaces & biophysical >Low-Temperature Heat Capacity and One-Dimensional Ferromagnetic Behavior of the Organic Free Radical 4-Benzylideneamino-2,2,6,6-tetramethylpiperidin-1-oxyl (BATMP)
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Low-Temperature Heat Capacity and One-Dimensional Ferromagnetic Behavior of the Organic Free Radical 4-Benzylideneamino-2,2,6,6-tetramethylpiperidin-1-oxyl (BATMP)

机译：有机自由基4-苯甲叉基氨基-2,2,6,6-四甲基哌啶-1-氧基（BATMP）的低温热容和一维铁磁行为

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摘要

Heat capacities of the organic free radical ferromagnet 4-benzylideneamino-2,2,6,6-tetramethylpiperidin-1-oxyl (BATMP) crystal were measured in the temperature range between 0.1 and 300 K by adiabatic calorimetry. A ferromagnetic phase transition was found at T_C = 0.19 K, and a broad heat-capacity anomaly was found arising from the short-range ordering above T_C characteristic of low-dimensional magnetic spin systems. The enthalpy and entropy gains due to both the magnetic phase transition and the heat-capacity anomaly were evaluated to be ΔH = 3.86 J mol~(-1) and ΔS = 5.64 J K~(-1) mol~(-1), respectively. The value of the experimental magnetic entropy agrees well with the theoretical value R ln 2 (5.76 J K~(-1) mol~(-1)) expected for a spin quantum number S = 1/2 spin system (R is the gas constant). The magnetic heat capacity hump due to the short-range order was well accounted for in terms of an S = 1/2 one-dimensional ferromagnetic Heisenberg model with the intrachain exchange interaction J/k_B = 0.95 K (k_B is Boltzmann's constant). This fact suggests that BATMP crystal is a one-dimensional ferromagnet above T_C. The spin wave analysis of the magnetic heat capacities below T_C revealed that BATMP crystal is in a three-dimensional ferromagnetic state below T_C and the averaged interchain exchange interaction is J'/k_B = 0.026 K.
机译：通过绝热量热法在0.1至300 K的温度范围内测量了有机自由基铁磁体4-亚苄基氨基-2,2,6,6-四甲基哌啶-1-氧基（BATMP）晶体的热容量。在T_C = 0.19 K处发现了铁磁相变，并且发现了由低维磁自旋系统的T_C特性以上的短程有序引起的宽容热异常。磁相变和热容异常引起的焓和熵增益分别为ΔH= 3.86 J mol〜（-1）和ΔS= 5.64 JK〜（-1）mol〜（-1）。 。实验磁熵的值与自旋量子数S = 1/2自旋系统的预期理论值R ln 2（5.76 JK〜（-1）mol〜（-1））吻合得很好（R是气体常数）。短程有序的磁热容峰很好地解决了S = 1/2一维铁磁海森堡模型，链内交换相互作用为J / k_B = 0.95 K（k_B是玻尔兹曼常数）。这个事实表明BATMP晶体是高于T_C的一维铁磁体。对T_C以下的磁热容量进行的自旋波分析表明，BATMP晶体在T_C以下处于三维铁磁状态，平均链间交换相互作用为J'/ k_B = 0.026 K.

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