Journal of the Korean Physical Society, Vol. 61, No. 4, August 2012, pp. 568∼574 Effect of Al Doping on the Cation Distribution in Copper Ferrite Nanoparticles and Their Structural and Magnetic Properties A. T. Raghavender ∗ Nanomagnetism Laboratory, Department of Physics and Astronomy, Seoul National University, Seoul 151-747, Korea Sagar E. Shirsath Department of Physics, Vivekanand College, Aurangabad 431001, India D. Pajic, K. Zadro and T. Milekovic Department of Physics, Faculty of Science, University of Zagreb, Bijenicka c. 32, HR-10000 Zagreb, Croatia K. M. Jadhav Department of Physics, Dr. Babasaheb Ambedkar Maratwada University, Aurangabad 431004, India K. Vijaya Kumar Department of Physics, Jawaharlal Nehru Technological University Hyderabad, College of Engineering, Nachupally, Karimnagar - 505 501, A.P., India (Received 23 March 2012, in final form 24 May 2012) Nanocrystalline CuFe2-xAlxO4 (0.0 ≤ x ≤ 1.0) was synthesized by using the sol-gel method and its structural and magnetic properties were investigated. The crystallite size was observed to decrease from 20 to 6 nm with increasing Al content. The lattice parameters were observed to decrease with increasing Al content. The cation distribution from X-ray intensity calculations revealed that Cu 2+ preferably occupied octahedral [B] sites. Al 3+ ions replaced the Fe 3+ ions in the tetrahedral (A) and the octahedral [B] sites. As a result the Fe 3+ concentration at (A) and [B] sites decreases, leading to a suppression of the long range magnetic ordering. Magnetic hysteresis loops were measured at room temperature with a maximum applied magnetic field of ≈1 T. As the Al 3+ content increases, the measured magnetic hysteresis curves become more and more narrow, and the saturation magnetization and the remanent magnetization both decrease. The reduction of magnetization with increasing of aluminum content is caused by non-magnetic Al 3+ ions and weakened interaction between sublattices. The reduction in the magnetization compared to the bulk may originate from the smallness of particles. This is also accompanied by a coercive field reduction. PACS numbers: 61.10.N2, 67.80.Gb, 75.60.-d Keywords: Nanoferrites, Cu-Al ferrite, Cation distribution, Magnetic properties DOI: 10.3938/jkps.61.568 I. INTRODUCTION Nanomaterials have been the subject of attention and imagination for scientists and engineers in the recent years. Nanosized structures make possible the design of materials with improved physical and chemical proper- ties that offer new properties compared to conventional materials [1]. Studies on spinel ferrites and their related structures have been the subject of interest due to their * E-mail: atraghavender@snu.ac.kr, raghavi9@gmail.com; Tel: +82-2-880-6603; Fax: +82-2-884-3002 special combination of physical properties and technolog- ical applications [2–4]. The magnetic properties of these ferrites depend largely on their structural features and on the distribution of the ions in the sub-lattices. Copper ferrite, CuFe 2 O 4 , can be described as closely packed arrangement of oxygen ions, with Cu 2+ and Fe 3+ ions at the tetrahedral (A) and the octahedral [B] sites [5]. The ionic configurations based on the preference en- ergies proposed by Miller [6] for individual cations in CuFe 2−x Al x O 4 suggests that Cu 2+ prefers to occupy B sites and that Al 3+ and Fe 3+ ions can occupy both A and B sites. Diamagnetic substitution in spinel ferrites is found -568-