On the Verwey Transition in Cu1+-Ion-Substituted Magnetite

다국어 초록 (Multilingual Abstract)

Slowly cooled CuxFe3.xO4 (x = 0.1, 0.2) has been investigated over a temperature range from 82
to 700 K by using the M¨ossbauer technique. After the samples are annealed under vacuum at 450
C for half an hour, the X-ray diffraction patterns have peaks associated with the magnetite and the
hematite phases. M¨ossbauer spectra reveal the conventional magnetite pattern with an additional
hematite pattern. Intensity ratios of B to A subspectra for the magnetite phase are 1.9 . 2.0 over
the entire temperature range, and the Cu ions are distributed over A and B sites randomly. The
ratios of the hematite intensity to the total intensity in the M¨ossbauer spectra for x = 0.1 and x =
0.2 are 10 and 21 %, respectively. These hematite ratios may be due to annealing under vacuum at
450 C, which transforms Cu2+ ionic states into Cu1+. The Verwey temperatures for x = 0.1 and
x = 0.2 are 123 ± 2 K and 128 ± 2 K, respectively. If the charge neutral condition is applied to
the magnetite phase of annealed sample, the Cu1+-substituted magnetite with a single-phase cubic
spinel structure is produced. The cationic distribution of the Cu1+-substituted magnetite has been
determined, and the Verwey transition of the Cu1+-substituted magnetite has been observed.