The effects of the iron content on structural and magnetic properties of Sr 0.80 La 0.20 Fe x Zn 0.15 O 19 hexagonal ferrites Yujie Yang, Xiansong Liu n , Dali Jin, Kai Huang, Shang Gao Engineering Technology Research Center of Magnetic Materials, School of Physics & Materials Science, Anhui University, Hefei 230601, Anhui, PR China article info Article history: Received 5 September 2013 Received in revised form 30 November 2013 Available online 22 December 2013 Keywords: Hexagonal ferrites Iron content La–Zn substitution Magnetic properties X-ray diffraction abstract The hexagonal ferrite Sr 0.80 La 0.20 Fe x Zn 0.15 O 19 (10.65 rx r12.05) magnetic powder and magnets were synthesized by the ceramics process. The phase components of the hexagonal ferrite magnetic powder were studied using X-ray diffraction (XRD). Scanning electron microscopy (SEM) was used to investigate the morphology of the sintered magnets. The effects of the iron content on magnetic properties of the magnets were studied systematically. The remanence (B r ) and maximum energy product [(BH) max ] for the magnets at x ¼11.25 reached the maximum value of 414.5 mT and 32.24kJ/m 3 , respectively. The intrinsic coercivity (H cj ) and magnetic induction coercivity (H cb ) for the magnets at x ¼11.65 reached the maximum value of 265.8 kA/m and 257.8 kA/m, respectively. & 2013 Elsevier B.V. All rights reserved. 1. Introduction The hexagonal ferrites are ceramic magnetic materials and have played an important role in many technological and industrial fields. Among various hexagonal ferrites, the M-type hexagonal ferrites have been widely used as permanent magnets, microwave devices, magneto-optics and magnetic recording media due to a low cost, outstanding chemical stability and large uniaxial magnetocrystalline anisotropy [1,2]. In order to fulfill various applications, many attempts have been made to improve the magnetic properties of M-type hexagonal ferrites by adding or doping some elements. La 3 þ substitution of Sr 2 þ and substitution of transition metals such as Zn 2 þ , Co 2 þ , Mn 2 þ , Ni 2 þ , Ti 2 þ and Ti 4 þ on the Fe 3 þ have been investigated [3–6]. On the other hand, M-type hexagonal ferrites with combined substitution such as La–Co, La–Zn, La–Cu, Co–Ti, and so on, were synthesized by sol–gel, rf diode sputtering or ceramic methods [7–15]. Partial substitution of Ba 2 þ –Fe 3 þ or Sr 2 þ –Fe 3 þ by La 3 þ –Zn 2 þ ions in M-type ferrites can lead to a change of the intrinsic magnetic properties [9–13]. Corral-Huacuz et al. prepared the La–Zn substituted barium ferrite powders by sol–gel and found out that La–Zn substitution could increase the saturation magne- tization and yield a more homogeneous microstructure and finer crystallite sizes [9]. Shen et al. prepared the La–Zn substituted strontium ferrite nanofibers by sol–gel and reported that a small amount of La–Zn substitution could increase the saturation magnetization and lead to a continuous reduction of the coercivity with the increase of La–Zn substitution [11]. Liu et al. synthesized the La–Zn substituted strontium ferrite thin films and pointed out that a proper amount of La–Zn substitution could improve the saturation magnetization [12]. However, no prior studies were carried out to investigate the La–Zn substituted hexagonal ferrites with different iron contents prepared by the ceramics process. In this paper, the hexagonal ferrite Sr 0.80 La 0.20 Fe x Zn 0.15 O 19 (10.65 rx r12.05) magnetic powder and magnets were synthe- sized according to the ceramics process. The effects of the iron content on the structure and magnetic properties of hexagonal ferrites Sr 0.80 La 0.20 Fe x Zn 0.15 O 19 have been studied systematically. 2. Experimental procedure The samples of hexagonal ferrite Sr 0.80 La 0.20 Fe x Zn 0.15 O 19 mag- netic powder and magnets were obtained using the ceramics process. Raw materials used in the present study were SrCO 3 (97% purity), La 2 O 3 (99% purity), Fe 2 O 3 (98% purity) and ZnO (99% purity). The raw materials were weighed in the nominal ratio in a stoichiometric composition of Sr 0.80 La 0.20 Fe x Zn 0.15 O 19 , where x varies from 10.65 to 12.05 with about 0.2 increment. Mixtures of these raw materials were milled in water for 6 h with an angular velocity of 80 rpm and a ball-to-power weight ratio of 12:1. The milling processes were performed in ball mill using hardened steel balls with diameter of 8 mm. The mixed power was dried, crushed, and sifted. These samples were made into balls of about Φ 8 mm, and the temperature was increased up to 1250 1C in a muffle; and then these balls were calcined for 2 h in air. The calcined samples Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/jmmm Journal of Magnetism and Magnetic Materials 0304-8853/$ - see front matter & 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.jmmm.2013.12.010 n Corresponding author. Tel./fax: þ86 551 65107674. E-mail address: xiansongliu@ahu.edu.cn (X. Liu). Journal of Magnetism and Magnetic Materials 355 (2014) 254–258