Effects of Cu and Co Substitution on the Properties of NiZn Ferrite Thin Films

Transcription

1 88 Effets of Cu and Co Substitution on the Properties of NiZn Ferrite Thin Films Le-Zhong Li, Long Peng, Xing-Hua Zhu, and Ding-Yu Yang Abstrat Cu- and Co-substituted NiZn ferrite thin films, Ni 0.4-x Zn 0.6 Cu x Fe 2 and Ni 0.5 Zn 0.5 Co x Fe 2-x (0 x 0.2), are synthesized by sol-gel proess. The rystallographi and magneti properties of Cu- and Co-substituted NiZn ferrite thin films have been investigated. The lattie parameter dereases with Cu substitution and inreases with Co The saturation magnetization dereases and the oerivity inreases with the inrease of Cu Moreover, the saturation magnetization gradually inreases with the inrease of Co substitution when x 0.10, but dereases when x>0.10. Meanwhile, the oerivity initially dereases with the inrease of Co substitution when x 0.10, but inreases when x>0.10. Index Terms Crystallographi property, Cu and Co substitution, magneti property, NiZn ferrite thin films, sol-gel proess. 1. Introdution The trend for downsizing eletroni equipments and the potential appliations of soft ferrite materials have lead to the fabriation of thin films of ferrites. NiZn ferrites exhibit favorable properties suh as high resistivity, low eddy urrent losses, and high saturation magnetization [1] [3], whih an be used for thin film devies of high frequeny. NiZn ferrite thin films have been prepared by different tehniques: sol-gel [4] [7], spin spray plating [8] [10], magnetron sputtering [11], pulsed-laser deposition [12], et. The sol-gel method adopted in this paper has the following advantages [13]. First, the omposition of films tends to be homogeneous and films possess high quality. Seond, the heat treatment temperature is low, and the mirostruture and mirorystallite size of thin films an be ontrolled by the annealing temperature. Last, the equipment is heap and Manusript reeived Deember 6, 2011; revised January 13, This work is supported by the Sientifi Researh Foundation of Chengdu University of Information Tehnology under Grant No. KYTZ Authors are with the College of Optoeletroni Tehnology, Chengdu University of Information Tehnology, Chengdu , China ( lezhongli@uit.edu.n). Color versions of one or more of the figures in this paper are available online at Digital Objet Identifier: /j.issn X the high vauum is not neessary. The properties of NiZn ferrites in the bulk materials an be modified by ions substitution and adding proper additives, suh as Mn 2+[14] [16], Cu 2+[17],[18], Bi 3+[19], W 6+[20],[21], Nb 5+[22] ions, et. In NiZn bulk ferrite, proper Cu 2+ ion onentrations an derease the magneti losses. Proper Co 2+ ion onentrations an improve the magneti properties beause of the positive value of magnetorystalline anisotropy onstant (K 1 ). But only a few works about the ompositions and preparation proesses have been done in the NiZn ferrite thin films [4] [13],[23], and the work about the Cu and Co substitution NiZn ferrite thin films synthesized by the sol-gel proess has hardly been aomplished. Therefore, this paper fouses on the rystallographi and magneti properties of Cu- and Co-substituted NiZn ferrite thin films. 2. Experimental Proedures 2.1 Preparation of NiZn Ferrite Thin Films The samples of Ni 0.4 x Zn 0.6 Cu x Fe 2 and Ni 0.5 Zn 0.5 Co x Fe 2 x (x=0, 0.05, 0.10, 0.15, 0.20) ferrite thin films were synthesized by sol-gel proess. Stoihiometri quantities of analytial grade Zn(CH 3 COO) 2 2H 2 O, Ni(CH 3 COO) 2 4H 2 O, Fe(NO 3 ) 3 9H 2 O, Cu(CH 3 COO) 2.H 2 O and Co(NO 3 ) 2 6H 2 O were first dissolved in 2-methoxyethanol to form a mixed solution. After the solution was stirred for 1 h, the aeti aid was added to adjust the onentration of the solution to 0.3 mol/l. Meanwhile, polyethylene glyol was added. As a kind of surfatant, it an effetively prevent the olloidal partiles of helate from being jointed with eah other. Then, the prepared solution was ontinuously stirred for 2 h and plaed at room temperature for 36 h to form the stable sol-gel preursors used for the following proesses. First, the wet films were deposited by a spin oating method on the substrate of SiO 2 glass at 4000 rpm for 30 s. Seond, the wet films were dried at C for 10 min to remove the mixed solvents. Third, the operation of spin oating and drying was repeated to get the required thikness of the films. Last, the dried films were heated at 400 C for 30 min to pyrolyze and exlude the organi substanes and then were annealed at 750 C (Cu substitution) and 700 C (Co substitution) for 1 h in air and ooled slowly in the furnae.

2 LI et al.: Effets of Cu and Co Substitution on the Properties of NiZn Ferrite Thin Films Charaterization and Property Measurements The phase identifiation of the thin films was performed by the Philips X Pert PRO X-ray diffratometer (XRD), with Cu Kα radiation. The magneti properties were measured by the TOEI VSM-5S-15 vibrating sample magnetometer (VSM) at room temperature. 3. Results and Disussion 3.1 Phase Charaterization X-ray diffration patterns of Cu- and Co-substituted NiZn ferrite thin films are shown in Fig. 1. The patterns math well with the harateristi refletions of ubi spinel struture and without unidentified extra peaks. The lattie parameter (a) of Cu- and Co-substituted NiZn ferrite thin films as a funtion of Cu and Co substitution (x) is shown in Table 1. The lattie parameter of the samples is alulated by using the relation: a = ( λ 4sin θ)( h + k + l ). From Table 1 we an see that the lattie parameter dereases from nm to nm with the inrease of Cu substitution, of whih the derease trend is well in aordane with the variations of Cu-substituted bulk NiZn ferrites [18]. Meanwhile, Table 1 indiates an inrease trend of the lattie parameter with Co substitution whih inreases from nm to nm. Intensity (a.u.) a Spinel phase x=0.20 x=0.10 Table 1: Variations of lattie parameter (a) of NiZn ferrite thin films with different Cu and Co substitutions. Ni 0.4 x Zn 0.6 Cu x Fe 2 Ni 0.5 Zn 0.5 Co x Fe 2 x x a (nm) It is well aknowledged that the divalent Cu 2+ and Co 2+ ions have a strong otahedral-site (B site) preferene [24]. The Cu 2+ and Co 2+ ions replae an equivalent number of Ni 2+ and Fe 3+ ions from B sites, respetively. The radius of the Cu 2+ ion (0.070 nm) is smaller than that of the Ni 2+ ion (0.078 nm) [24]. So, the lattie parameter of NiZn ferrite thin films dereases with the inrease of Cu The radius of the Co 2+ ion (0.082 nm) is bigger than that of the Fe 3+ ion (0.067 nm) [24]. Thus, Co 2+ ion enters into the otahedral-site (B site) whih swells the lattie, and then enlarges the lattie parameter. 3.2 Mirostruture Observation Fig. 2 shows the surfae morphologies of Ni 0.3 Zn 0.6 Cu 0.1 Fe 2 and Ni 0.5 Zn 0.5 Co 0.1 Fe 1.9 ferrite thin films. It demonstrates that the grain size of films is symmetrial and uniform with Cu and Co 3.3 Magneti Properties The hysteresis loops of Ni 0.4 Zn 0.6 Cu 0.1 Fe 2 and Ni 0.5 Zn 0.5 Co 0.1 Fe 1.9 ferrite thin films are shown in Fig. 3. From it we an see that all the samples are magnetized to saturation when the external field is less than Oe. a b x=0.00 Intensity (a.u.) b θ( ) 2θ ( ) (a) Spinel phase x=0.20 x=0.10 x= θ 2θ( ) (b) Fig. 1. X-ray diffration patterns of (a) Cu-substituted NiZn ferrite thin films and (b) Co-substituted NiZn ferrite thin films. (a) (b) Fig. 2. SEM images of Ni 0.3 Zn 0.6 Cu 0.1 Fe 2 (a) and Ni 0.5 Zn 0.5 Co 0.1 Fe 1.9 (b) ferrite thin films. Ms (emu/ m 2 ) Ms (emu/m 3 ) Ni 0.5 Zn 0.5 Co 0.1 Fe 1.9 Ni 0.3 Zn 0.6 Cu 0.1 Fe H (Oe) Fig. 3. Hysteresis loop of Cu- and Co-substituted NiZn ferrite thin films with x=0.10.

3 B 90 Fig. 4 shows the saturation magnetization (M s ) and oerivity (H ) of thin films as a funtion of Cu substitution ( x). M s dereases and H inreases with the inreasing Cu Aording to Miller s site preferene energies of ions [25], the ations distribution of films an be written as follows: (Zn 0.6 Fe 0.4 )[Ni 0.4 x Cu x Fe 1.6 ]. (A site) (B site) Aording to Neel model, the magneti moment of Ni 0.4 x Zn 0.6 Cu x Fe 2 ferrite thin films is alulated by the following equation: M = MB -MA = 8.8 -x (1) where M A and MB are the magneti moments in the A and B sites, and the magneti moments of Zn 2+, Ni 2+, Cu 2+, and Fe 3+ ions are 0, 2, 1, and 5 μb, respetively [24]. So, the magnetization of B sublattie (M B ) will be dereased with 2+ inrease of lower magneti moment of Cu. This will make a net derease in the magnetization whih eventually results in the derease of M s. Furthermore, M s and H of thin films as a funtion of Co substitution (x) are shown in Fig. 5. M s gradually inreases with the inrease of Co substitution when x 0.10, and dereases when x>0.10. Meanwhile, H hanges ontrarily. Ms (emu/m 2 ) Ms (emu/m 3 ) Ni 0.4-x Zn 0.6 Cu x Fe Ms s H x H (Oe) H (Oe) Fig. 4. Variations of Ms and H of Ni 0.4 x Zn 0.6 Cu x Fe 2 ferrite thin films with different x. s (emu/m 2 ) Ms (emu/m 3 M 330 Ni 0.5 Zn 0.5 Co x Fe 2-x Ms s H x H (Oe) H (Oe) Fig. 5. Variations of M s and H of Ni 0.5 Zn0.5CoxFe2 x ferrite thin films with different x. In fat, magneti properties of ferrites are influened by many fators, inluding the struture, omposition, defets, and internal stress. The inreasing Co substitution leads to the derease of antiparallel Fe 3+ ions in B site, and the magneti moments of Fe 3+ ion (5 μb) is bigger than Co 2+ ion (3 μb), whih make M B inrease. On the other hand, the value of magnetorystalline anisotropy onstant (K 1 ) of Co 2+ ion is positive, those of NiZn ferrites are negative, and using ompensation of negative and positive values an make K 1 0, whih means the magnetorystalline field reahes the minimum. So, M s gradually inreases with the inrease of Co substitution when x With the further inrease of Co substitution, antiparallel Co 2+ ions inrease in B site, and magnetorystalline anisotropy onstant beomes positive, whih makes the magnetorystalline field inrease. Meanwhile, the exess Co substitution ontent will introdue the larger internal stresses [26]. Finally, M s dereases with the inrease of Co substitution when x>0.10. H of ferrite thin films is related to the saturation magnetization by the relation: H 1 M [24] s. Aording to this relation, with the inrease of Cu substitution, H would derease with the derease of M s (Fig. 4). Moreover, H gradually dereases with the inrease of Co substitution when x 0.10, and inreases when x>0.10 (Fig. 5). 4. Conlusions Co substitution NiZn ferrite thin films, Ni0.5Zn 0.5 Co x Fe 2 x (0 x 0.2), have been synthesized by a sol-gel method. The struture and magneti properties of thin films have been investigated and the following results have been obtained: 1) The lattie parameter dereases with the inrease of Cu substitution and inreases with the inrease of Co 2) M s dereases and H inreases with the inrease of Cu 3) M s gradually inreases with the inrease of Co substitution when x 0.10, and dereases when x>0.10. Meanwhile, H hanges ontrarily. Referenes [1] J. Gao, Y. Cui, and Z. Yang, The magneti properties of Ni x Zn 1 x Fe 2 films fabriated by alternative sputtering tehnology, Materials Siene and Engineering: B, vol. 110, no. 2, pp , 4. [2] T. Kiyomura and M. Gomi, Room-temperature epitaxial growth of Ni-Zn ferrite thin films by pulsed laser deposition in high vauum, Japanese Journal of Applied Physis, vol. 36, no. 2, pp. L1000 L1002, 1997.

4 LI et al.: Effets of Cu and Co Substitution on the Properties of NiZn Ferrite Thin Films 91 [3] Z. Beji, S. Ammar, L. S. Smiri, M. J. Vaulay, F. Herbst, B. Gallas, and F. Fiévet, Spray deposition of nanorystalline Ni 1 x Zn x Fe 2 (x 0.6) films from polyol-mediated sol: Mirostruture and magneti properties, Journal of Applied Physis, vol. 103, no. 7, pp. 07E744 07E746, 8. [4] A. S. Albuquerque, J. D. Ardisson, and W. Maedo, A study of nanorystalline NiZn-ferrite SiO 2 synthesized by sol gel, Journal of Magnetism and Magneti Materials, vol. 192, no. 2, pp , [5] F. Liu, T.-L. Ren, C. Yang, L. Liu, A.-Z. Wang, and J. Yu, NiCuZn ferrite thin films for RF integrated indutors, Materials Letters, vol. 60, no. 11, pp , 6. [6] S.-Y. Bae, C.-S. Kim, and Y.-J. Oh, Magneti properties of sol-gel derived Ni-Zn ferrite thin films on yttria stabilized zironia buffered Si(100), Journal of Applied Physis, vol. 85, no. 8, pp , [7] P. Gao, E. V. Rebrov, and T. Verhoeven, Strutural investigations and magneti properties of sol-gel Ni 0.5 Zn 0.5 Fe 2 thin films for mirowave heating, Journal of Applied Physis, vol. 107, no. 4, pp , [8] N. Matsushita, T. Nakamura, and M. Abe, Spin-sprayed Ni-Zn-Co ferrite films with high μ r >>100 in extremely wide frequeny range 100 MHz-1 GHz, Journal of Applied Physis, vol. 93, no. 10, pp , 3. [9] C.-M. Fu, H.-S. Hsu, and Y.-C. Chao, High-frequeny transport properties of spin-spray plated Ni Zn ferrite thin films, Journal of Applied Physis, vol. 93, no. 10, pp , 3. [10] T.-H. Hai, H. Van, T. Phong, and A. Masanori, Spinel ferrite thin-film synthesis by spin-spray ferrite plating, Physia B: Condensed Matter, vol. 327, no. 2 4, pp , 3. [11] M. Desai, S. Prasad, N. Venkataramani, I. Samajdar, A. K. Nigam, N. Keller, R. Krishnan, E. M. Baggio-Saitovith, B. R. Pujada, and A. Rossi, Anomalous variation of oerivity with annealing in nanorystalline NiZn ferrite films, Journal of Applied Physis, vol. 91, no. 10, pp , 2. [12] C. N. Chinnasamy, S. D. Yoon, A. Yang, A. Baraskar, C.Vittoria, and V. G. Harris, Effet of growth temperature on the magneti, mirowave, and ation inversion properties on NiFe 2 thin films deposited by pulsed laser ablation deposition, Journal of Applied Physis, vol. 101, no. 9, pp. 09M M517-3, 7. [13] K. Sun, Z.-W. Lan, Z. Yu, and X.-L. Nie, Charaterization and magneti properties of polyethylene glyol modified NiZn ferrite thin films, Current Applied Physis, vol. 11, no. 3, pp , [14] J.-H. Nam, W.-G. Hur, and J.-H. Oh, The effet of Mn substitution on the properties of NiCuZn ferrites, Journal of Applied Physis, vol. 81, no. 8, pp , [15] B. Li, Z.-X. Yue, X.-W. Qi, J. Zhou, Z.-L. Gui, and L.-T. Li, High Mn ontent NiCuZn ferrite for multiplayer hip indutor appliation, Materials Siene Engineering: B, vol. 99, no. 1 3, pp , 3. [16] Z.-X. Yue, J. Zhou, Z.-L. Gui, and L.-T. Li, Magneti and eletrial properties of low-temperature sintered Mn-doped NiCuZn ferrites, Journal of Magnetism and Magneti Materials, vol. 264, no. 2 3, pp , 3. [17] H. Su, H.-W. Zhang, X.-L. Tang, Y. Jing, and Y.-L. Liu, Effets of omposition and sintering temperature on properties of NiZn and NiCuZn ferrites, Journal of Magnetism and Magneti Materials, vol. 310, no. 1, pp , 7. [18] M. Ušáková, J. Lukáč, R. Dosoudil, E. Ušák, J. Sláma, J. Šubrt, J. Lukáč, and A. Grusková, I nfluene of Cu 2+ ions on strutural and magneti properties of NiZn ferrites, Journal of Materials Siene: Materials in Eletronis, vol. 18, no. 12, pp , 7. [19] J. Mürbe and J. Töpfer, Ni-Cu-Zn Ferrites for low temperature firing: II. Effets of powder morphology and Bi 2 O 3 addition on mirostruture and permeability, Journal of Eletroeramis, vol. 16, no. 3, pp , 6. [20] K.-S. Park, J.-H. Nam, and J.-H. Oh, Magneti properties of NiCuZn ferrites with addition of tungsten trioxide, Journal of Magnetism and Magneti Materials, vol , no. 2, pp , 1. [21] H. Su, H.-W. Zhang, and X.-L. Tang, Effets of CuO, MoO 3 and WO 3 dopping on magneti properties of NiZn ferrites, Chinese Journal of Materials Researh, vol. 19, no. 5, pp , 5. [22] K. Sun, Z.-W. Lan, Z. Yu, L.-Z. Li, and J.-M. Huang, Grain growth and magneti properties of Nb 2 O 5 -Doped NiZn ferrites, Japanese Journal of Applied Physis, vol. 47, no. 10, pp , 8. [23] Y. Shimada, N. Matsushita, M. Abe, K. Kondo, T. Chiba, and S. Yoshiba, Study on initial permeability of Ni-Zn ferrite films prepared by the spin spray method, Journal of Magnetism and Magneti Materials, vol. 278, no. 1 2, pp , 4. [24] Y.-J. Huang, S.-K. Li, and Z.-W. Lan, Magneti Materials, Chengdu: UESTC Press, 1993, pp (in Chinese). [25] A. Miller, Distribution of ations in spinels, Journal of Applied Physis, vol. 30, no. 4, pp. S24 S25, [26] A. D. Giles and F. F. Westendorp, The effet of obalt substitutions on some properties of manganese zin ferrites, Journal of Physis D: Applied Physis, vol. 9, no. 14, pp , Le-Zhong Li was born in Shandong Provine, China, in He reeived the Ph.D. degree in materials siene from University of Eletroni Siene and Tehnology of China (UESTC) in 9. Now, he works with the Chengdu University of Information Tehnology. His researh interests inlude magnetism and magneti materials, and LTCC tehnology.

5 92 Long Peng was born in Sihuan Provine, China, in He reeived the M.S. degree in materials siene and tehnology from the Southwest University of Siene and Tehnology (SWUST) in 6, and the Ph.D. degree in eletroni siene and tehnology from UESTC. Now, he works with the Chengdu University of Information Tehnology. His researh interests inlude magnetism and magneti materials, mirowave materials and passive devies, and LTCC tehnology. Xing-Hu Zhu was born in Sihuan, China, in He reeived the M.S. degree in materials physis and hemistry and Ph.D. degree in materials physis and hemistry from Sihuan University, Chengdu, China, in 1 and 6, respetively. Now, he works with the Chengdu University of Information Tehnology as an assoiate professor. His urrent researh interests are in the areas of optoeletroni materials and devies for detetor, imager, display, and energy onversion tehnology. Ding-Yu Yang was born in Guizhou, China, in He reeived the M.S. degree in semiondutor physis and Ph.D. degree in materials physis and hemistry from Lanzhou University, Lanzhou, China, in 3 and Sihuan University, Chengdu, China, in 9, respetively. Now, he works with the Chengdu University of Information Tehnology as an assoiate professor. His urrent researh interests are in the areas of optoeletroni materials and devies for detetor, imager, display, and energy onversion tehnology.