Diamagnetic anisotropy of silicates composed of tetrahedral networks

Small diamagnetic anisotropy, (Delta chi)(DIA), on the order of 10(-9) to 1 0-(10) emu/g was detected for four silicates by the use of the field-induce d harmonic-oscillation method in the high-temperature region. The measured Delta chi-T relations were effective to separate the Delta chi component ca used by the paramagnetic impurity ions. The obtained maximum (Delta chi)(DI A) values between two magnetic principal axes are (2.1+/-0.1)x10(-9) emu/g [b-a axes] for orthoclase, (3.5+/-0.1)x10(-9) emu/g [b-a axes] for petalite , (0.8+/-0.1)x10(-9) emu/g [a-e axes] for scapolite and (3.8+/-0.1)x10(-9) emu/g [a-e axes] for apophyllite. The (Si,Al)O-4 tetrahedral frameworks com posing the crystal structures of the silicates are considered to be the ori gin of the observed (Delta chi)(DIA) values.