Hyperfine couplings between the paramagnetic moment and nuclei in the metallic phase of low silica X zeolite loaded with potassium

Abstract

Temperature dependences of NMR spectra have been observed for ²³Na and ²⁷Al in the metallic phase of Na–K form low silica X (LSX) zeolite loaded with potassium, where the condition of saturation is achieved with a loading level of 9.0 atoms per supercage and the paramagnetic moment contributes to the magnetism of the system beyond simple isolated spin. Two separated peaks have been recognized for ²³Na, where the shift values show a quite linear relationship with susceptibility, and the so-called K–χ plot works quite well to give values of 0.32 kOe μ_B⁻¹ and 0.40 kOe μ_B⁻¹ for hyperfine coupling constants. Although no separated peak is seen in the ²⁷Al NMR spectrum, the spectral centroid deviates to the positive side. The shoulder of the spectrum scales to susceptibility and the K–χ plot also works well to give a value of 0.15 kOe μ_B⁻¹ for the hyperfine coupling constant. The orbital of potassium-originated electrons confined in the cage of LSX is understood as seeping out over the framework of zeolite, which is wider than that of the sodium-originated case.