Insulator-to-metal transition and magnetism of potassium metals loaded into regular cages of zeolite LSX

Abstract

Zeolite LSX (low-silica X) crystals have an aluminosilicate framework with regular supercages and β-cages. They are arrayed in a double diamond structure. The loading density of guest K atoms per supercage (or β cage), n, can be controlled from 0 to ≈ 9. At n 6. These properties are explained by the polaron effect including the electron correlation. Ferrimagnetic properties are observed at n ≈ 9. A remarkable increase in the resistivity is observed at very low temperatures at n ≈ 9, and is discussed in terms of the hypothesis of a Kondo insulator.