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Magnetic measurement of Fe3−
x
Si
x
O4 spinel solid solutions indicates that their Curie temperatures decrease gradually, but not linearly, from 851 to 12 K with
increasing content of nonmagnetic ions Si4+. Magnetic hysteresis becomes more noticeable in solid solutions having a larger content of Fe2SiO4. Saturation magnetizations of Fe3−
x
Si
x
O4 samples increase up to x=0.357 and they are easily saturated in the field of H=0.1 T. However, magnetization of the sample of x=0.794 does not approach saturation even at high field of H=7.0 T and has a large coercive force. The Si4+ disordered distribution is confirmed to be tetr[Fe3+
1−
x
+
x
t
Si4+
x
(1−
t
)] octa[Fe2+
1+
x
Fe3+
1−
x
−
x
t
Si4+
x
t
] O4 by the spin moment, which is consistent with site occupancy obtained from X-ray crystal structure refinement. Their molecular
magnetizations would be expressed as M
B={4(1+x)+10xt}μB as functions of composition parameter x and Si4+ ordering parameter t of the solid solution. The sample of x=0.794 is antiferromagnetic below the Néel temperature, mainly due to the octahedral cation interaction M
O–M
O, while both M
T–M
O and M
O–M
O interactions induce a ferrimagnetic property. Concerning magnetic spin configuration, in the case of x>0.42, the lowest dɛ level becomes a singlet, resulting in no orbital angular momentum.
Received: 20 April 2000 / Accepted: 11 September 2000 相似文献
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