Anomalous low-temperature heat capacity in antiperovskite compound
Anomalous low-temperature heat capacity in antiperovskite compound
复制标题
反钙钛矿化合物的反常低温热容
DOI：
10.1088/1674-1056/26/2/026501
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发表时间：
2017
影响因子：
1.7
通讯作者：
Sun Yu-Ping
中科院分区：
文献类型：
--
作者：
Guo Xin-Ge;Lin Jian-Chao;Tong Peng;Lin Shuai;Yang Cheng;Lu Wen-Jian;Song Wen-Hai;Sun Yu-Ping
研究了反钙钛矿化合物axm3 （A= Al, Ga, Cu, Ag, Sn， X= C， N， M= Mn, Fe, Co）的低温热容。18种化合物的(C−γT)/ t3相对于T均有较大的峰值，表明存在Debye t3定律所未预料到的低能声子模式。该峰值对80koe （1 Oe= 79.5775 a·m−1）外磁场不敏感。对于晶格常数较小的化合物，随着峰高的降低，峰向更高的温度移动。反钙钛矿化合物的(C−γT)/ t3与T的异常峰可能是由较重的A原子引起的强色散声分支和xm6八面体动态旋转产生的类光学模式引起的。这种低能声子模式可能不会对axm3化合物的正常热膨胀产生负影响，而在开放结构材料（如zrw2o8， scf3）中通常伴随着负热膨胀。
The low-temperature heat capacities are studied for antiperovskite compounds AXM 3 (A= Al, Ga, Cu, Ag, Sn, X= C, N, M= Mn, Fe, Co). A large peak in (C− γT)/T 3 versus T is observed for each of a total of 18 compounds investigated, indicating an existence of low-energy phonon mode unexpected by Debye T 3 law. Such a peak is insensitive to the external magnetic field up to 80 kOe (1 Oe= 79.5775 A· m− 1). For compounds with smaller lattice constant, the peak shifts towards higher temperatures with a reduction of peak height. This abnormal peak in (C− γT)/T 3 versus T of antiperovskite compound may result from the strongly dispersive acoustic branch due to the heavier A atoms and the optical-like mode from the dynamic rotation of XM 6 octahedron. Such a low-energy phonon mode may not contribute negatively to the normal thermal expansion in AXM 3 compounds, while it is usually concomitant with negative thermal expansion in open-structure material (eg, ZrW 2 O 8, ScF 3).(paper)