科研之友
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摘要
We have performed electron spin resonance (ESR) studies of K-4(3+) and (K3Rb)(3+) nanoclusters incorporated in powder specimens of aluminosilicate sodalite at several microwave frequencies between 9 and 34 GHz. The K-4(3+) and (K3Rb)(3+) clusters are arrayed in a bcc structure and are known to show antiferromagnetic ordering below the Neel temperatures of T-N similar or equal to 72 and similar or equal to 80 K, respectively, due to the exchange coupling between s electrons confined in the clusters. We have found sudden broadenings of ESR spectra in both samples below TN. The line shape of the spectra below T-N is analyzed by powder pattern simulations of antiferromagnetic resonance (AFMR) spectra. The calculated line shapes well reproduce the experimental ones at all the frequencies by assuming a biaxial magnetic anisotropy. We have evaluated extremely small anisotropy fields of approximately 1 Oe indicating that these materials are ideal Heisenberg antiferromagnets. We have also found that the magnetic anisotropy changes from easy- plane type to uniaxial type by changing into a heavier alkali- metal cluster and that the g value shifts to a large value beyond two below T-N for K-4(3+) and (K3Rb)(3+) nanoclusters. These novel features of K-4(3+) and (K3Rb)(3+) nanoclusters incorporated in sodalite are discussed.
- 出版日期2013-11-4
