COEXISTENCE OF DOUBLE ALTERNATING ANTIFERROMAGNETIC CHAINS IN (VO)2P2O7 : NMR STUDY
COEXISTENCE OF DOUBLE ALTERNATING ANTIFERROMAGNETIC CHAINS IN (VO)2P2O7 : NMR STUDY
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(VO)2P2O7 中双交替反铁磁链的共存：核磁共振研究
DOI：
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发表时间：
1999
期刊：
影响因子：
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通讯作者：
Y. Ueda
中科院分区：
文献类型：
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作者：
J. Kikuchi;K. Motoya;T. Yamauchi;Y. Ueda
测量了自旋为1/2的交替链化合物（VO）_2P_2O_7中~（31）P和~（51）V核的核磁共振谱。通过对~（31）P核磁共振谱的温度变化分析，发现（VO）_2P_2O_7具有两个独立的自旋分量，它们具有不同的自旋能隙。由31 P和51 V位的位移随温度的变化关系确定了自旋能隙为35 K和68 K，这与最近的非弹性中子散射实验[A.W.加勒特等人，物理修订信函79，745（1997）]。这表明（VO）_2P_2O_7是由两个磁子系统组成的，这两个磁子系统表现出不同的磁激发，这与沿B轴沿着方向的两个晶体学上不等价的V链有关。磁链间自旋能的差异是由于磁链间V-V距离的微小差异造成的，这可能导致磁链间交换交替的不同。根据交换相互作用与原子间距离的经验关系，估计并讨论了每个交替链中的交换相互作用。
Nuclear magnetic resonance (NMR) of 31P and 51V nuclei has been measured in a spin-1/2 alternating-chain compound (VO)_2P_2O_7. By analyzing the temperature variation of the 31P NMR spectra, we have found that (VO)_2P_2O_7 has two independent spin components with different spin-gap energies. The spin gaps are determined from the temperature dependence of the shifts at 31P and 51V sites to be 35 K and 68 K, which are in excellent agreement with those observed in the recent inelastic neutron scattering experiments [A.W. Garrett et al., Phys. Rev. Lett. 79, 745 (1997)]. This suggests that (VO)_2P_2O_7 is composed of two magnetic subsystems showing distinct magnetic excitations, which are associated with the two crystallographically-inequivalent V chains running along the b axis. The difference of the spin-gap energies between the chains is attributed to the small differences in the V-V distances, which may result in the different exchange alternation in each magnetic chain. The exchange interactions in each alternating chain are estimated and are discussed based on the empirical relation between the exchange interaction and the interatomic distance.