Anomalous magnetization of potassium clusters incorporated into zeolite A at high magnetic field

Magnetization process of potassium clusters arrayed in cages of zeolite A (framework type code LTA) is measured up to 52 T by using a pulsed magnet. This material is known to show ferromagnetism at certain numbers of guest potassium atoms (or s-electrons) per cluster. We observe an anomalously large magnetization at higher fields at low temperatures. The level crossing of LS multiplet terms in the degenerate 1p-like orbital of potassium cluster is discussed as a possible origin of the anomalous increase in the magnetization at higher fields