The Magnetic and Semiconducting Properties of CoFe₂O₄-ZnFe₂O₄，and CoFe₂O₄-Co₃O₄ Polycrystals

Abstract

The peculiar behaviour of Zn2＋ion and Co3＋ion in ferrite was studied in relation to the magnetic and semiconducting Propertie3．(1) CoFe204(feπimagnetism)一ZnFe20 (antiferromagnetism)When the density of cation vacancies increased，the coercive force and the induced anisotropy constant increased and conductivity decreased． The composition at maximum saturatiQn magnetization cGrrespo敬de迅 to the minimum conductiv呈ty，and the maximum activation energy of the conductivity，to maximum the induce4 anisotropy constant。(2) CoFe20る(ferrimagnetism)一Co80 (paramagnetism) The sample wasρ一type semiconductor due to the formation of an excess of Co8＋i㎝． Its conductivity wαs about10一601cm and smaller than that of CoFe20 ． The activation eneτgy of c㎝ductiαn wa8about O．4-0．5eV．The mobility was smaller than that o壬CoFe204by four factors． The magnetic cooli㎎爾ect c㎝1d be explained in terms of the electron diffusion m㏄hanism between Co2＋ion and Co8＋ion． These phenomena described above are explained by the low spin state of Co8＋． 1 1ntroduction The author1)旬7)has been studying the relationship between the magnetic and semiconducting properties of ferrite， The following results have been obtained． (1) Sintering Polycrysta11)-3)(Co藩Fe3_露04)； The coercive force increased，and the saturation mag且etization and conductivity decreased with increase in the sintering oxygen partial pressure at a given￠within the range of O．8≦諾≦1．0， It can be explained that by changing the sintering oxygen partial pressure，the cation vacancies at the16d site 駄re fonned wit｝1increase in oxygen pressure． (2) Single crystal filπ旧4》-7)(Fe30べCoFe204， CoFe204-ZnFe204，MnFe20べZnFe204)3 They were prep＆red epitaxially up電)n(100)，(110)