Sains Malaysiana 25(1): 51-57 (1996)                                                                           Sains Fizik dan Gunaan/

Physical and Applied Sciences

Anomalous Temperature Dependence of Electrical

Resistivity in Mg_0.6Zn_0.4Fe₂O₄ Ferrite

Mustafa Hj. Abdullah & Ahmad Nazlim Yusoff

Jabatan Fizik

Fakulti Sains Fizis & Gunaan

Universiti Kebangsaan Malaysia

43600 UKM Bangi, Selangor D.E. Malaysia

SYNOPSIS

The  electrical resistivity of Mg_0.6Zn_0.4Fe₂O₄ ferrite was measured as a function of temperature in the range 300-630 K. Two anomalies are observed in the resistivity curves for measurements during heating up. These anomalies are identified as a magnetic anomaly at the Neel temperature, T_N = 598 K, while the other one at T_Ot = 445 K is discussed as due to the contribution of conduction from the tetrahedral sites. The anomaly at Tot was reduced in the measurements during recooling, while the anomaly at T_N was disappeared completely during recooling and second cycle. These effects are discussed as due to the increase of Fe²⁺ ions at the octahedral sites as a result of cation redistribution at higher temperatures. A relatively small anomaly at T_ot still can be observed during the second run. This is possible if the Fe²⁺ ions have a preference to be relocated at the tetrahedral sites at lower temperatures.

SINOPSIS

Kerintangan elektrik Mg_0.6Zn_0.4Fe₂O₄ ferit telah diukur sebagai fungsi suhu dalam julat 300 - 630 K. Dua anomali dapat dicerap pada lengkung kerintangan bagi pengukuran semasa pemanasan. Dua anomali tersebut dikenalpasti sebagai anomali magnet pada suhu Neel, T_N = 598 K, manakala yang satu lagi pada T_ot = 445 K dibincangkan sebagai berpunca daripada sumbangan kekonduksian pada tapak tetrahedron. Anomali pada T_ot mengurang dalam pengukuran semasa penyejukan semula pada julat suhu yang sarna, manakala anomali pada T_N terus lenyap dalam pengukuran semasa penyejukan semula dan juga semasa kitar kedua. Kesan ini dibincangkan sebagai disebabkan oleh peningkatan ion Fe²⁺ pada tapak oktahedron daripada proses taburan semula kation pada suhu tinggi. Anomali yang berkurang pada T_ot masih boleh dicerap semasa pengukuran kitar kedua. Keadaan seperti ini adalah mungkin jika ion Fe²⁺ mempunyai kecenderongan untuk bertempat semula pada tapak tetrahedron apabila suhu menurun.

RUJUKAN/REFERENCES

Ahmed, M. A., El Nimr, M. K., Tawfik, A. & Abodata, A. M. 1988. Effect of magnetic order on the conductivity in Co-Zn ferrites. Journal of Material Science Letters 7: 639.

Brabers, V. A. M., Proykova, Y. G., Salerno, N. & Whall, T. E. 1987. Anomalous electrical properties of  M_xFe_3-xO₄.  Journal of Applied Physics 61: 4390.

Gani, A. A. & Miryasov, N. M. 1972. Effect of transition from the ferrimagnetic to the paramagnetic state on the conductivity of Cu- Cd ferrites. Soviet Physics Solid State13: 2627.

Lotgering, F. K. 1964. Semiconduction and cation valencies in manganese ferrite. Journal of Physics and Chemistry of Solid 25: 95.

Mousa, M. A., Summan, A. M., Ahmed, M. A. & Badawy, A. M. 1989. Electrical conduction in  γ - irradiated and unirradiated Fe₃O₄, CdFe₂O₄ and Co_xZn_1-xFe₂O₄ (0 < x < 1) ferrites. Journal of Material Science 24: 2478.