- Charge Transformation of CU-ions in CuxFe3-xO4 (χ=0.1, 0.2)
- ㆍ 저자명
- Lee. Choong Sub,Lee. Chan Young,Kwon. Dong Wook
- ㆍ 간행물명
- Journal of magnetics
- ㆍ 권/호정보
- 2002년|7권 2호|pp.25-28 (4 pages)
- ㆍ 발행정보
- 한국자기학회
- ㆍ 파일정보
- 정기간행물| PDF텍스트
- ㆍ 주제분야
- 기타
Slowly cooled $Cu_xFe_{3-x}O_4$ ($chi$=0.1, 0.2) have been investigated over a temperature range from 82 to 700 K using the M$ddot{o}$ssbauer technique. X-ray diffraction shows that these have a single-phase cubic spinel structure of lattice parameters $alpha$=8.396 and 8.398${AA}$, respectively. Since Cu ions prefer B (octahedral) sites to A (tetrahedral) sites, the ionic distribution is $(Fe)_A[Fe_{2-x}Cu_x]_BO_4$. M$ddot{o}$ssbauer spectra consisted of two sets of 6-line pattern from. A site in ferric state and B site in ferrous-ferric state. Intensity ratio of B to A subspectra is 1.0 at 82 K and increases to 2.0 at 700 K with increasing temperature. After annealing the samples under vacuum at $450^circ{C}$ for a half hour, x-ray diffraction patterns have the peaks of magnetite- and hematite-phase. Lattice constants of magnetite-phase are 8.395 and 8.392 ${AA}$ smaller than 8.396 and 8.398 ${AA}$ before annealing, respectively. M$ddot{o}$ssbauer spectra reveal the conventional magnetite pattern with the additional hematite pattern. Intensity ratios of B to A subspectra fur magnetite-phase become 1.9-2.0 over all temperature ranges and Cu ions are distributed over A and B sites randomly. Ratios of hematite to total intensity in M$ddot{o}$ssbauer spectra for $chi$= 0.1 and $chi$= 0.2 are 10 and 21%, respectively. These hematite ratios may be due to annealing under vacuum at $450^circ{C}$, which transforms $Cu^{2+}$ ionic states into $Cu^{1+}$. Verwey temperatures far $chi$= 0.1 and $chi$= 0.2 are $123pm2$ K and $128pm2$ K.