Sains Ma1aysiana 25(2): 1-15 (1996)                                                                              Sains Fizis dan Gunaan/

                                                                                                                                       Physical and Applied Sciences

Sifat Magnet dan Elektrik Ferit Mn_0.6-zMg_zZn_0.4Fe₂O₄

(Magnetic and electrical properties of Mn_0.6-zMg_zZn_0.4Fe₂O₄ ferrites)

Ahmad Nazlim Yusoff & Mustaffa Hj. Abdullah

Jabatan Fizik, Fakulti Sains Fizis dan Gunaan

Universiti kebangsaan Malaysia

43600 UKM Bangi, Selangor, D.E. Malaysia

ABSTRAK

Sistem ferit Mn_0.6-zMg_zZn_0.4Fe₂O₄ (z = 0, 0.1, 0.2, 0.3, 0.4, 0.5 dan 0.6) disediakan melalui kaedah tindakbalas keadaan pepejal. Pembelauan sinar-X (XRD) mengesahkan kesemua sampel berstruktur spinel fasa tunggal. Analisa data XRD menunjukkan pemalar kekisi (a) dan ketumpatan XRD (r_XRD) yang berkurang dengan penggantian Mn oleh Mg. Sistem ferit ini menunjukkan pemagnetan maksimum pada suatu komposisi Mg. Kebolehtelapan awal (µ_i) meningkat bagi sampel dengan pemagnetan yang tinggi manakala koersiviti (H_c) berubah sebaliknya. Kerintangan elektrik arus terus (ρ_at) pada 300 K diukur untuk sampel yang disepuh lindap dan yang tidak disepuh lindap. Nilai kerintangan elektrik pada 300 K untuk sampel dengan z = 0.3, 0.4, 0.5 dan 0.6 didapati lebih rendah berbanding dengan yang lain. Perubahan kerintangan elektrik terhadap suhu dalam satu kitar (300 K---680 K---300 K) bagi sampel yang tidak disepuh lindap menunjukkan anomali pada suhu Neel (T_N) dan suatu anomali di sekitar suatu suhu (T_ot). Anomali pada T_ot dicerap semasa pengukuran suhu meningkat dan semakin jelas untuk sampel dengan kandungan Mg yang tinggi. Anomali tersebut lenyap untuk pengukuran suhu menurun dan pengukuran bagi sampel yang disepuh lindap kecuali untuk z = 0.6. Kewujudan anomali tersebut dibincangkan sebagai berpunca daripada sumbangan kekonduksian pada tapak tetrahedron dan taburan semula kation-kation di antara dua tapak interstis A dan B. T_N ditentukan daripada lengkung kerintangan melawan suhu untuk sampel yang disepuh lindap dan didapati meningkat dengan kandungan Mg. Kesemua sampel menunjukkan tenaga pengaktifan ferimagnet (E_f) yang lebih kecil daripada tenaga pengaktifan paramagnet (E_p ).

ABSTRACT

Samples of Mn_0.6-zMg_zZn_0.4Fe₂O₄ ferrites (z = 0, 0.1, 0.2, 0.3, 0.4, 0.5 and 0.6) were prepared by solid state reaction. X-ray diffraction (XRD) confirmed the formation of a single phase spinel structure. Analysis of XRD data indicates that the lattice parameter (a) and XRD density (ρ_XRD) decrease with the substitution of Mn by Mg. This ferrite system indicates a maximum magnetization at a certain composition of Mg. The initial permeability (µ_i) increases for samples with higher magnetization, while the coercivity vary in the opposite manner. DC resistivity (ρ) at 300 K was obtained for annealed an unannealed samples. It is seen that the resistivities at 300 K for samples with z = 0.3, 0.4, 0.5 and 0.6 are lower than the others. The electrical resistivity as a function of temperature in one complete cycle (300 K---680 K---300 K) for unannealed samples indicates anomalies at Neel temperature (T_N) and around a certain temperature (T_ot). Anomaly at T_ot can be seen during heating run and is greater for samples with higher Mg content. The anomaly is absent during cooling run and for the annealed samples except for Z = 0.6. The existence of this anomaly is discussed as due to a contribution of conductivity from the tetrahedral sites and cation redistribution between the two interstitial A and B sites. T_N was determined from the variation of resistivity with temperature for the anealed samples and is seen to increase with increasing Mg content. The ferrimagnetic activation energy (E_f) is smaller than the paramagnetic activation energy (E_p) for all samples.

RUJUKAN/REFERENCES

Abd El-Ati, M. 1., Kafafy, A.M. & Tawfik, A. 1991. Magnetic properties of zinc doped ferrites. Act. Phys. Pol. 79: 889.

Brabers, V.A.M., Proykova, Y.G., Salerno, N. & Whall, T.E. 1987. Anomalous electrical properties of Mn_xFe_3-xO₄ J. Appl. Phys. 61(8): 4390.

Chandra, P.R. & Baijal, J.S. 1985. Electrical conductivity of Ni-Zn Ferrites doped with Ti⁴⁺ ions. J. Less-Common Met. 106: 257.

Cullity, B.D. 1967. Element of X-ray diffraction. USA: Addison-Wesley Publishing Compony, Inc.

Cullity, B.D. 1972. Introduction to magnetic materials. USA: Addison-Wesley Publishing Company, Inc.

Hastings, J.M. & Corliss, L. M. 1956. Neutron diffraction study of manganess ferrite.           Phys. Rev. 104(2): 328.

Lotgering, F.K. 1964. Semiconduction and cation valencies in manganese ferrites. J. Phys. Chem. Solids 25: 95.

Mazen, S. A., Abd-EI-Rahiem, A.E. & Sabrah, B.A. 1988. Effect of Mg²⁺-Fe³⁺ replacement of physical and electrical properties of the system Mg_xZn_0.3Fe_(2.7-x) O₄ + d. 1. Mater. Sci. Lett. 23: 2917.

Rezlescu, N. & Cuciureanu, E. 1970. Cation distribution and Curie temperatures in the copper-manganese-zinc ferrites. J. Phys. Chem. Solids. 32: 1096.

Rodriguesz, J. & Fontcuberta, J. 1987. Quatitative analysis of a Fe₃O₄ + Li_xFe₃O₄ sample by the X-ray reitveld method. J. Mater Sci. 22: 1001.

Sawant, S.R. & Patil, R.N. 1982. Cation distribution, magnetization and electrical switching in Cu_xZn_1-xFe₂O₄ system. Indian J. Phys. 56A: 233.

Slick, P.I. 1980. Ferrites for none microwave application. Holland: North-Holland Publishing Company.

Thorp, S, Muhammad-Ahmad, M.E. & Savage, C. 1987. Curie temperatures of magnesio-ferrite precipitates in heat-treated Fe/MgO. J. Mater. Sci. Lett. 6: 1341.

Wolska, E. & Eiedel, E. 1992. Intermediate phases produced during the formation of cadminium-nickel ferrites. Powder Diffraction 7: II.