EPR study of the x, α and β structures of lithium phthalocyanine
EPR study of the x, α and β structures of lithium phthalocyanine
复制标题
酞菁锂x、α、β结构的EPR研究
DOI：
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发表时间：
1998
期刊：
影响因子：
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通讯作者：
J. André
中科院分区：
文献类型：
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作者：
M. Brinkmann;P. Turek;J. André
用电子顺磁共振（EPR）方法研究了酞菁锂自由基的x、α和β晶体结构的磁性。不同的磁性行为（磁化率，线形）证明在PcLi粉末和解释的分子堆积。在平均场温度TCW约为0.001 ℃时，α相的居里-外斯磁化率随温度的升高而增大。4.5±1 K，而x相（在乙腈中生长的粉末）必须考虑双组分磁化率，涉及居里-外斯贡献（TCWca. -3 1 K）和热活化贡献，活化能Ea约为。0.04 EV.对于PcLi β结构，可以区分两个温度域：当T>50 K时，居里-外斯磁化率，平均场温度TCW约为100 K。在-60 ℃ ~ 5 K时，T<20 K时，TCWca具有Curie-Weiss型磁化率。-7 1 K占优势。的整体磁性能的PcLi多晶型物进行了讨论，在麦康奈尔的铁磁性和反铁磁性在固体自由基的机制。研究了β-PcLi针的磁性（磁化率、自旋扩散各向异性）。吸附氧在55 K以下强烈地改变β-PcLi微晶和粉末的线形、线宽和g因子各向异性。
The magnetic properties of the lithium phthalocyanine radical are investigated for the x,α and β crystal structures via electron paramagnetic resonance (EPR). Different magnetic behaviours (susceptibility, line shape) are evidenced in PcLi powders and interpreted in terms of the molecular packing. A Curie–Weiss susceptibility is observed for the α-phase with a mean-field temperature, TCW of ca. 4.5±1 K, whereas a two-component susceptibility must be considered for the x-phase (powders grown in acetonitrile) involving a Curie–Weiss contribution (TCWca. –3±1 K) and a thermally activated contribution with an activation energy Ea of ca. 0.04 eV. For the PcLi β structure two temperature domains can be distinguished: for T>50 K a Curie–Weiss susceptibility with a mean-field temperatureTCW of ca. –60±5 K is observed while for T<20 K a Curie–Weiss-like susceptibility withTCWca. –7±1 K dominates. The overall magnetic properties of the PcLi polymorphs are discussed in terms of McConnell’s mechanism for ferromagnetism and antiferromagnetism in solid free radicals. The magnetic properties of β-PcLi needles (magnetic susceptibility, anisotropy of spin diffusion) have been investigated. Adsorbed oxygen is shown to alter strongly the line shape, the linewidth and the g-factor anisotropy in β-PcLi crystallites and powders at temperatures below 55 K.