Magnetic properties of Ca-containing zeolite low-silica X loaded with K atoms

It is known that an N-type ferrimagnetic order with the highest Curie temperature \(\varvec{T_C}\) ${\mathit{T}}_{\mathit{C}}$ of about 20 K occurs when K metal is loaded into porous zeolite crystal of low silica X (LSX), which originally contains both Na \(^+\) ${}^{+}$ and K \(^+\) ${}^{+}$ ions. To control the magnetic sublattices of the ferrimagnetism in this material, we substitute the Na \(^+\) ${}^{+}$ ions with Ca \(^{2+}\) ${}^{2+}$ ions and loaded with K atoms. A metallic transition was observed in electron spin resonance with increasing the K-loading density. This can be attributed to the itinerant electrons provided by the guest K atoms in the supercage network of LSX. Ferromagnetic magnetization is observed below about 3 K for the metallic samples. This is similar to the Ca-free and pure K system, which exhibits ferrimagnetism, but the spontaneous magnetization is more than 10% smaller in the Ca-containing system. In addition, the higher \(\varvec{T_C}\) ${\mathit{T}}_{\mathit{C}}$ N-type ferrimagnetic order disappeared. The deep potential of Ca causes the magnetic moment in the \(\beta \) $\beta$ -cage of LSX to disappear, which is expected to suppress the overall magnetic order.