Cryst. Res. Technol. 45, No. 1, 89 – 93 (2010) / DOI 10.1002/crat.200900550 © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim X-ray diffraction and magnetization studies of BiFeO 3 multiferroic compounds substituted by Sm 3+ , Gd 3+ , Ca 2+ Mansour Al-Haj* Physics Department, Mutah University, Mutah, Jordan Received 15 September 2009, accepted 12 October 2009 Published online 30 October 2009 Key words multiferroics, X-ray diffraction, magnetization, transition temperature. PACS 61.66.Fn, 61.05.cp, 75.60.Ej The multiferroic compounds Bi 0.9 Sm 0.1 FeO 3 , Bi 0.9 Gd 0.1 FeO 3 , Bi 0.9 Ca 0.1 FeO 3 , Bi 0.9 Sm 0.05 Ca 0.05 FeO 3 , and Bi 0.9 Gd 0.05 Ca 0.05 FeO 3 were prepared by the conventional ceramic method and were characterized by X-ray diffraction, vibrating sample magnetometry, and differential scanning calorimetry. The compounds were found to have the rhombohedral perovskite-like structure, accompanied by a small residual Bi 2 Fe 4 O 9 impurity phase. Magnetic hysteresis loops with enhanced remnant magnetization and coercive field were obtained for the Gd-containing compounds. The improvement of magnetic behavior of the Gd-containing compounds is thought to arise mainly from the partial suppression of the spiral spin structure and the stronger interaction between magnetic ions. The magnetic transition temperatures of the compounds were found to be in the range 300-310 °C. © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim 1 Introduction Multiferroics are materials which simultaneously exhibit electric and magnetic ordering and are candidates for multifunctional device applications. BiFeO 3 (BFO) has a rhombohedrally distorted perovskite structure with space group R3c. It is a G-type canted antiferromagnetic with a transition temperature T N ≅ 370 °C and a ferroelectric with a transition temperature T C ≅ 830 °C, which make it a candidate multiferroic material for various applications. In addition, it was shown recently that BFO has at least four magnetic transitions [1]. However, due to its spatially modulated spiral spin structure, any net magnetization cannot be observed at room temperature. Besides that, impurity phases and large leakage current density are major obstacles associated with this compound. Structure modification and improvement of electrical and magnetic properties of BFO were achieved by minor substitution of Bi 3+ by ions such as Dy 3+ [2,3], Sm 3+ [4,5], La 3+ [6,7], Nd 3+ [8,9], Gd 3+ [10,11], Y 3+ [12], Ca 2+ , Sr 2+ , Pb 2+ , Ba 2+ [13-16], by minor substitution of Fe 3+ by ions such as Cr 3+ [17], Co 3+ [18], Mn 3+ [19,20], Ti 4+ [21], or by simultaneous minor substitution of Bi 3+ and Fe 3+ by ions such as La 3+ and V 5+ , respectively [22]. Various methods, besides the conventional one, were used for material synthesis such as sol-gel auto- combustion [2], metal ion complex precursor solution [9,12], and hydrothermal [18,23]. The mechanism by which ion substitution affects the magnetic properties of BFO is not completely understood, and further research work is still required for a better understanding of this system. For this reason, we explore in this work the structure and magnetism of the compounds Bi 0.9 Sm 0.1 FeO 3 , Bi 0.9 Gd 0.1 FeO 3 , Bi 0.9 Ca 0.1 FeO 3 , Bi 0.9 Sm 0.05 Ca 0.05 FeO 3 , and Bi 0.9 Gd 0.05 Ca 0.05 FeO 3 . For brevity, we will refer to these compounds by BSFO, BGFO, BCFO, BSCFO, and BGCFO, respectively. 2 Experimental The samples were prepared by the solid state reaction method. Pure oxides of Bi 2 O 3 , Sm 2 O 3 , Gd 2 O 3 , Fe 2 O 3 , CaO were weighed, mixed, and ground in an agate mortar and pestle. The mixtures were then calcined at ____________________ * Corresponding author: e-mail: mansour@mutah.edu.jo