Zn Materiales

Materials Letters 59 (2005) 26 – 31 www.elsevier.com/locate/matlet

Magnetic studies of Zn–Ti-substituted barium hexaferrites prepared by mechanical milling
A. Gonzalez-Angelesa,*, G. Mendoza-Suareza, A. Gruskovab, M. Papanovab, J. Slamac ´ ´ ´ ´
b a Cinvestav-Saltillo, Carr. Saltillo-Mty. Km. 13, P.O. Box 663, 25000 Saltillo, Coahuila, Mexico ´ Department of Electrotechnology, Faculty ofElectrical Engineering and Information Technology, Slovak University of Technology, Ilkovicova 3, ˇ 812 19 Bratislava, Slovak Republic c Department of Electromagnetic Theory, (FEEIT-SUT), Slovak Republic

Received 14 May 2004; received in revised form 27 August 2004; accepted 11 September 2004 Available online 27 September 2004

Abstract Barium hexaferrite fine particles with compositionBaFe12À2x Znx Tix O19 (0VxV0.6) were obtained by mechanical milling. The effect of Zn–Ti substitution on the magnetic properties and microstructure of the powders were investigated by Mfssbauer spectroscopy, XRD, vibrating sample magnetometry (VSM), scanning electron microscopy (SEM) and thermomagnetic analysis. The particle size reached a minimum at x=0.2 and then increased with the substitution level,reaching a value of 102.96 nm. Mfssbauer studies revealed that Zn2+ ions replace Fe3+ ions on tetrahedral sites (4f1), while Ti4+ preferred the octahedral sites (4f2 and 2a). D 2004 Elsevier B.V. All rights reserved.
PACS: 74.25Ha; 75.50.-y; 33.45+x Keywords: Magnetic properties; Zn–Ti doped Ba-ferrite; Mfssbauer spectra

1. Introduction Nowadays, the need of new magnetic materials explains theconsiderable interest of researchers on the study of hexagonal ferrites, due to their applications in new emerging technologies. Those technological applications require materials with strict control of the microstructure which governs the extrinsic magnetic behavior, such as homogeneity, particle size and shape [1]. To obtain good quality of M-type ferrites, several methods have been used tomodify their magnetic and structural properties, which are strongly dependent on the synthesis method used [2]. The physical properties needed are partly fulfilled by obtaining materials free of intermediate phases and adequate cation substitution.

* Corresponding author. Tel.: +52 844 438 9600; fax: +438 6910. E-mail address: alvaro.gonzalez@cinvestav.udu.mx (A. Gonzalez-Angeles). ´ 0167-577X/$ -see front matter D 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.matlet.2004.09.012

Different cations or cation combinations have been used to substitute the BaM Fe3+ ions to reduce its grain size and high magnetic uniaxial anisotropy field without affecting M s, for applications in high-density magnetic recording and microwave absorption devices [3]. It has been shown that Zn–Ticationic mixtures produce materials with suitable characteristics for high-density magnetic recording [4,5]. Also, it has been reported that site preference of Zn2+ ions can provoke an increase in the saturation magnetization, M s, and reduce the switching field distribution (SFD) of the particles, which is an important parameter in magnetic recording applications [6]. On the other hand, the replacementof iron ions by Ti 4+ on 4f2 site can also increase M s. As part of an extensive investigation on magnetic properties, grain size and cationic distribution of substituted ferrites, this paper reports the magnetic properties, grain size and cationic distribution of Zn–Ti

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mode. The g-ray source was 57Co in a rhodium matrixand the Mfssbauer spectra were fitted employing the NORMOS software. The magnetic properties at room temperature were measured in a vibrating sample magnetometer Lake Shore 7300 vibrating sample magnetometry (VSM) with an external magnetic field applied up to 12 kOe. The temperature dependence of the magnetic susceptibility, v(h), was measured using the bridge method in alternating magnetic...