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D-和L-丙氨酸的低温磁相变——磁场变化下的比热和直流磁化率(英文)
引用本文:王文清,沈新春,龚.D-和L-丙氨酸的低温磁相变——磁场变化下的比热和直流磁化率(英文)[J].物理化学学报,2010,26(10):2597-2603.
作者姓名:王文清  沈新春  龚
作者单位:1. Beijing National Laboratory for Molecular Sciences, Department of Applied Chemistry, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, P. R. China; 2. School of Materials Science&Engineering, Beijing Institute of Fashion Technology, Beijing 100029, P. R. China
基金项目:国家重点基础研究发展规划项目(973),国家自然科学基金 
摘    要:为了解D-和L-丙氨酸单晶晶格在极低温下是否存在磁手性相变,在2-20 K下改变磁场强度(0,1,3,5T)测定其比热.实验结果表明比热和温度之间的函数关系很好地符合C(T)=aT3+b/T2方程,其中aT3项为晶格声子的贡献,可由公式CV=(12/5)π4R(T/ΘD)3来描述(ΘD为德拜温度),b/T2项为磁场对比热的贡献.实验发现,在2-20 K范围内D-和L-丙氨酸单晶在不同磁场强度下均存在Boson峰(在Cp/T3-T曲线中表现为一个最大值).磁的贡献导致D-和L-丙氨酸单晶的四条Cp/T3-T曲线在2-12 K时不重合,且在12-20 K时消失,此即Schottky反常.零磁场下,D-和L-丙氨酸的Boson峰分别为9.44和10.86 K;德拜温度分别为151.5和152.7 K.结合磁场强度1 T下的直流磁化率测定,发现在温度低于5 K时,D-和L-丙氨酸单晶有相反的磁化率行为,反映了核自旋和电子自旋弱相互作用的手性表现.

关 键 词:磁相变  D-和L-丙氨酸  比热  直流磁化率  Boson    德拜温度  
收稿时间:2010-03-19
修稿时间:2010-09-27

Cryogenic Magnetic Transition of D-and L-Alanine:Magnetic Field Dependence of Specific Heat and DC Magnetic Susceptibility
WANG Wen-Qing,SHEN Xin-Chun,GONG Yan.Cryogenic Magnetic Transition of D-and L-Alanine:Magnetic Field Dependence of Specific Heat and DC Magnetic Susceptibility[J].Acta Physico-Chimica Sinica,2010,26(10):2597-2603.
Authors:WANG Wen-Qing  SHEN Xin-Chun  GONG Yan
Institution:1. Beijing National Laboratory for Molecular Sciences, Department of Applied Chemistry, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, P. R. China; 2. School of Materials Science&Engineering, Beijing Institute of Fashion Technology, Beijing 100029, P. R. China
Abstract:To understand the intrinsic asymmetries of D-and L-alanine crystal lattices,the magnetic field dependence of zero-field and 1,3,and 5T on the heat capacity were measured from 2 to 20 K.The obtained heat capacity data shows linear behavior that follows:C(T)=aT3+b/T2.The first aT3 term is from the lattice phonon contribution with Cv=(12/5)π4R(T/⊙D)3 (⊙D is the Debye temperature).The second b/T2 term in the fitting formula is the magnetic contribution.In this experiment,the obtained Cp data for the D-and L-alanine single crystals show a Boson peak,which is seen as a maximum in the Cp/T3 versus Tplots in the low temperature region from 2-20 K at different fields.The four Cp/T3 versus T curves show a split between D-and L-alanine from 2-12 K and this is due to the magnetic contribution.This is absent between 12 and 20 K,which indicates the Schottky anomaly.The temperature of the Boson peak is 9.44 K for D-alanine and 10.86 K for L-alanine,and ⊙D is 151.5 and 152.7 K for D-alanine and L-alanine in zero-field,respectively.DC magnetic susceptibility data show the chiral behavior in nuclear spin-electron spin hyperfine interaction at very low temperature.
Keywords:Magnetic transition  D-and L-alanine  Heat capacity  DC magnetic susceptibility  Boson peak  Debye temperature
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