Magnetic property of potassium clusters in pressure-doped zeolite A

The pressure-doping technique was developed for further loading of guest potassium metal into porous crystals of zeolite beyond the upper limit at ambient pressure. A doping pressure dependence of the magnetic property of potassium clusters in cages of zeolite A is measured up to 320 MPa. The Curie constant monotonically decreases with increase in the doping pressure and shows very small values above 250 MPa. The magnetic susceptibility at 2 K, however, gradually increases and has a peak at 200 MPa. Observed decrease in the Curie constant is explained by the increase in the loading density of potassium. Simultaneously, the increase in the magnetic susceptibility at 2 K is explained by the superparamagnetism of ferromagnetic domains. A possible mechanism of change in the magnetic properties is discussed. (c) 2006 Elsevier B.V. All rights reserved.