Static and dynamic magnetic characteristics of BaCo 0.5 Mn 0.5 Ti 1.0 Fe 10 O 19 Saeed Choopani à , Neda Keyhan, Ali Ghasemi, Ali Sharbathi, Iman Maghsoudi, Mohammad Eghbali Electroceramic Research Center, Department of Physics, Malek Ashtar University of Technology, Shahhin Shahr, Iran article info Article history: Received 28 April 2008 Received in revised form 13 December 2008 Available online 13 January 2009 Keywords: Magnetic property Microstructure Susceptibility Reflection loss abstract The effect of Mn 2+ Co 2+ Ti 4+ substitution on microwave absorption has been studied for BaCo 0.5 Mn 0.5- Ti 1.0 Fe 10 O 19 ferrite–acrylic resin composites in frequency range from 12 to 20 GHz. X-ray diffraction (XRD), scanning electron microscope (SEM), vibrating sample magnetometer, AC susceptometer and vector network analyzer were used to analyze the structural, magnetic and microwave absorption properties. The results showed that the magnetoplumbite structures for all samples have been formed. Based on microwave measurement on reflectivity, BaCo 0.5 Mn 0.5 Ti 1.0 Fe 10 O 19 may be a good candidate for electromagnetic compatibility and other practical applications at high frequency. & 2009 Elsevier B.V. All rights reserved. 1. Introduction The increase in electromagnetic pollution due to the rapid development of gigahertz (GHz) electronic systems and telecom- munications has resulted in a growing and intense interest in electromagnetic-absorber technology. Electromagnetic interfer- ence (EMI) can cause severe interruption of electronically controlled systems. It can cause device malfunctions, generate false images, increase clutter on radar and reduce performance because of system-to-system coupling. These are some of the reasons why the use of self generated electromagnetic radiation apparatuses, which include cellular telephones, wireless compu- ters and pagers, are strictly prohibited in certain areas; for example, in hospitals, banks, petrol stations and inside airplanes. To overcome the problems created by EMI, electromagnetic wave absorbers with the capability of absorbing unwanted electro- magnetic signals, are used; and research on their electromagnetic and absorption properties is still being carried out [1,2]. Recent developments in microwave absorber technology have resulted in materials with high wave absorption coefficient, good physical performance and lower production cost [3,4]. There are a variety of absorber materials that can be used to suppress EMI depending on whether or not they are suitable for low and high frequency application [5–9]. As far as thickness and working frequency bandwidth are concerned, magnetic composites have obvious advantages. The magnetic fillers often used in such composites are ferrite materials such as spinel ferrites and hexaferrites [10,11]. Hexaferrites with planar magnetic anisotropy are greatly used as electromagnetic wave absorbers in GHz range. Barium ferrite powders are ideal fillers for the development of electromagnetic attenuation materials at microwave due to their low cost, low density, high stability, large electrical resistively and high micro- wave magnetic loss [12–15]. Many works have been reported on barium ferrites for use as electromagnetic materials [16–21]. In our previous paper [17–19], the microwave attenuation properties studied different doped ferrites. Here, we will report on the relationship between magnetic properties and microstructure for BaCo 0.5 Mn 0.5 Ti 1.0 Fe 10 O 19 . The magnetic properties and micro- wave absorbing characteristics were investigated. The reason for choosing this substitute compound is their different static magnetic properties (especially, the coercivity and saturation magnetization) at the critical substitution ratio for in-plane anisotropy [20,21]. The predicated reflection loss demonstrates that BaCo 0.5 Mn 0.5 Ti 1.0 Fe 10 O 19 may be a good candidate for wave absorbing materials with low reflectivity at microwave frequency. 2. Experimental 2.1. The preparation of ferrite powders The M-type barium ferrite with BaCo 0.5 Mn 0.5 Ti 1.0 Fe 10 O 19 composition was carried out with a conventional powder fabrication. The sample was synthesized from stoichiometric mixture of Fe 2 O 3 , TiO 2 , Co 3 O 4 , BaCO 3 and MnCO 3 . The mixture was crushed for 2h and calcined in air at 1160 1C for 8 h. The heating rate of sample was from room temperature to 600 1C with 6 1C/ min, and it was kept at 3 1C/min to the final sintering temperature. Calcined ferrite was crushed again for 5 h. The prepared powders are in the range 1–4 mm. ARTICLE IN PRESS Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/jmmm Journal of Magnetism and Magnetic Materials 0304-8853/$ - see front matter & 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.jmmm.2008.12.030 à Corresponding author. Tel.: +98 3125227796; fax: +98 312 5225068. E-mail address: saeedphy@yahoo.com (S. Choopani). Journal of Magnetism and Magnetic Materials 321 (2009) 1996–2000