Communications in Theoretical Physics
The quantum Sherrington-Kirkpatrick (SK) S = 1 spin-glass model with uniaxial anisotropy in applied magnetic field is investigated numerically. The dependences of entropy, specific heat and susceptibility on temperature are calculated for different magnetic fields. The dependence of specific heat on temperature exhibits the typical spin-glass characteristics. It is found that the susceptibility depends strongly on the sign of uniaxial anisotropy constants.
关键词:
anisotropy
Journal of Physical Chemistry A
The temperature dependence of magnetic susceptibility and sublattice magnetizations were calculated for a Heisenberg Hamiltonian of an S = 1 and S = 1/2 antiferromagnetic alternating spin chain by means of the many-body Green's function theory to show the possible occurrence of a ferrimagnetic phase transition for genuinely organic molecule-based magnets. The S = 1 site in the chain is composed of two S = 1/2 spins coupled by a finite ferromagnetic interaction. From the calculated results, it is found that the sublattice magnetization at low-spin S = 1/2 sites changes its sign from negative to positive with increasing temperature, giving rise to the spin alignments along the chain changing from anti ferromagnetic to ferromagnetic ones, which indicates that there is a magnetic phase transition occurring. Because of the weak intermolecular anti ferromagnetic interactions, the curves of the magnetic susceptibility multiplied by temperature (chi T) against temperature show a round peak at low temperatures, which is well consistent with recent experimental observations, and the ferrimagnetic phase transition could only be detected at an ultralow-temperature region and under very weak,external magnetic fields in practical organic materials. From the analysis of the sublattice magnetizations, it is uncovered that the appearance of the low-temperature peak in the curves of the chi T originates from the ferromagnetic spin alignments for all the spins along the chain, and the intermolecular antiferromagnetic interactions play a pivotal role in ferrimagnetic spin alignments of the magnetic systems. It is also found that the higher spatial symmetry of the intermolecular antiferromagnetic interactions have contributions to stabilize the ferrimagnetic ordering state in the molecule-based magnetic materials.
关键词:
nitrophenyl nitronyl nitroxide;simple classical pictures;numerical-calculations;composite molecules;magnetic-properties;building-blocks;ground-state;component;model;system
余庚华
,
仲嘉琪
,
王谨
,
詹明生
量子电子学报
doi:10.3969/j.issn.1007-5461.2012.03.001
Ba原子是光频标的候选者之一,对其进行有效的激光冷却与囚禁需要相关能级的寿命和跃迁几率的信息.Ba原子激发态6s6p3P1能级在激光冷却实验中很重要,通过Hanle效应实验测量了这一能级的寿命和自发辐射率,从理论和实验上研究了探测激光有限线宽和光强对Ba原子基态6s21S0与激发态6s6p3P1之间跃迁(波长791nm)Hanle效应荧光信号的影响.在考虑了激光线宽和光强因素后所得到的激发态6s6p3P1的能级寿命和自发辐射率与其他方法给出的结果符合很好.
关键词:
光谱学
,
能级寿命
,
Hanle效应
,
线宽
,
Ba原子
,
原子频标
韩文静
,
阿古拉
,
赵丽佳
,
白音孟和
人工晶体学报
以1,4-丁二胺为溶剂合成两种硫属化合物(1,4-DABH2)2Sn2S6·(1,4-DAB)(1)和(1,4-DABH2) Sb4S7(2)(1,4-DAB =1,4-丁二胺),单晶X-射线衍射分析表明化合物1为单斜晶系,空间群为P21/c,a=1.0862(5) nm,b=1.3053(6) nm,c=1.0283(5) nm,β=101.20(2)°,V=1.4302(12) nm3,Z=2;化合物2为三斜晶系,空间群为P-1,a=0.6009(4) nm,b =0.8989(7) nm,c=1.6548(12) nm,α =89.774(12)°,β=86.481 (12)°,γ=84.495(12)°,V=0.8880(11)nm3,Z=2.化合物1由离散的[Sn2S6]2+、质子化的有机胺和未质子化有机胺组成.化合物2是由质子化的有机胺和双链的[Sb4S7]2-离子组成的二维层状化合物.紫外-可见漫反射光谱研究结果表明,化合物1和2的禁带宽度分别为1.80 eV和1.54 eV,均为半导体.
关键词:
溶剂热合成
,
锡/锑硫属化合物
,
晶体结构
,
表征
邱元进
,
杨方
,
刘正才
,
林永辉
,
刘素珍
色谱
doi:10.3724/SP.J.1123.2012.01020
建立了畜禽产品中维吉尼亚霉素M1和S1药物残留检测的液相色谱-串联质谱分析方法.样品以甲醇-乙腈溶液(1:1,V/v)提取,上清液经0.01 mol/L磷酸二氢铵溶液稀释后,Oasis HLB固相萃取小柱净化,Luna C18色谱柱分离,以乙腈和含0.1％(体积分数)甲酸的5 mmol/L乙酸铵水溶液作为流动相进行梯度洗脱,电喷雾正离子模式电离(ESI+).多反应监测(MRM)模式检测,外标法定量.该方法对两物质线性范围均为0.15～10.O μg/L,相关系数r2均大于0.999；定量下限均为0.25 μg/kg.在不同基质中,0.25、0.50、2.5 μg/kg 3个添加水平的平均回收率范围为71.2％～98.4％,精密度范围为3.6％～15.4％.该方法具有快速简便、灵敏度高、准确性强等特点,适用于畜禽产品中维吉尼亚霉素的检测.
关键词:
液相色谱-串联质谱(LC-MS/MS)
,
维吉尼亚霉素M1
,
维吉尼亚霉素S1
,
残留
,
畜禽产品
Zeitschrift Fur Physik B-Condensed Matter
By means of the generalized static replica symmetric spin glass theory, a quantum Heisenberg S=1/2 spin glass model with the infinite-ranged random Dzyaloshinskii-Moriya (DM) interaction and ferromagnetic coupling is investigated. The dependence of entropy, specific heat, susceptibility and the corresponding order parameters on temperature is studied numerically for different ferromagnetic interactions and fixed anisotropy. Two spin glass phases has been found including transverse and mixed spin glass phases. It has been shown that the local susceptibility exhibits double-cusp features for different ferromagnetic coupling (J(0)). Phase transition poins are found in the specific heat-temperature plane at various ferromagnetic coupling values. Additionally, the dependence of the spontaneous moment on temperature is calculated.
关键词:
uniaxial anisotropy;transverse field;transition;model;alloys;state
孙清池
,
左孝杰
,
徐庭献
,
王裕斌
兵器材料科学与工程
doi:10.3969/j.issn.1004-244X.2001.03.002
研究了软性铌锑-锆钛酸铝Pb(Sb1/2 Nb1/2)ZrTiO3(简称SN)系及硬性锑锰-锆钛酸铅Pb(Mn1/3 Sb2/3)ZrTiO3(简称MS)系压电陶瓷电场E3和应变S1的关系.压电方程为S1=d31 E3,在弱电场下为线性关系.随着电场增加,压电应变系数d31变大,从而不再是常数.当电场E3增大到某一值时d31有极大值,我们称此电场为饱和电场Es.软性SN三元系压电陶瓷的退极化电场Ed为12.7kV/cm,小于它的矫顽场Ec(13.6kV/cm)以及d31极大值(-457pC/N)时的饱和电场Es(14kV/cm).而硬性MS三元系压电陶瓷的退极化电场Ed和d31极大值(-202pC/N)时的饱和电场Es相等,均为24kV/cm,大于它的矫顽电场Ec(18.6kV/cm).软性SN三元系压电陶瓷在较低的电场下就可产生很大的应变.而硬性MS三元系压电陶瓷可以施加很大的反向电场.
关键词:
压电应变系数D31
,
退极化电场Ed
,
矫顽电场Ec
,
饱和电场Es
,
电滞回线
黄利元
,
方卯发
量子电子学报
doi:10.3969/j.issn.1007-5461.2008.04.009
研究了一个处在均匀外磁场中的包含四个量子比特的各向同性海森堡XY模型中,两个间隔的量子比特之间的量子热纠缠,并用并发度来量度.这个模型包含两种量子比特:自旋为1/2的量子比特和自旋为S的量子比特.结果表明,外磁场可以引起两个间隔的量子比特之间的量子热纠缠.热纠缠的幅度与自旋S,温度T以及均匀外磁场B有关.因此,可以通过调节B的取值来控制热纠缠.当S足够大时,阈值温度也可能很高.这个特性可以被用于研究凝聚态系统的热纠缠,并且在固体系统进行量子信息研究中也将发挥很大的作用.
关键词:
量子光学
,
热纠缠
,
并发度
,
量子信息
