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Spread of interaction in nanocomposite hard/soft nanostructured magnets

In this study, the magnetic properties of 3D modeled two-phase hard/soft nanocomposite nanostructured magnets were simulated by means of the Monte-Carlo method. The dependences of the energy product and coercivity on the grain size and magnetically soft phase content were investigated. | Journal of Science and Technology 54 (1A) (2016) 9-16 SPREAD OF INTERACTION IN NANOCOMPOSITE HARD/SOFT NANOSTRUCTURED MAGNETS Nguyen Trung Hieu*, Nguyen Van Vuong Institute of Materials Science, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet, Cau Giay, Hanoi, Vietnam * Email: hieunt@ims.vast.vn Received: 05 September 2015; Accepted for publication: 15 December 2015 ABSTRACT In this study, the magnetic properties of 3D modeled two-phase hard/soft nanocomposite nanostructured magnets were simulated by means of the Monte-Carlo method. The dependences of the energy product and coercivity on the grain size and magnetically soft phase content were investigated. The influence of the interaction spreading in the soft phase on the magnetic properties was also discussed. The obtained results revealed that the energy product reaches an optimal value when the soft phase content ranges around 50 vol.%, and a strong magnetic interaction spreading locally along the Kneller-Hawig exchange length seems to be more important than a weak but widely spreading interaction. Keywords: 3D simulation, nanocomposite magnets, Monte-Carlo method, two-phase magnetically hard and soft, hardening interaction. 1. INTRODUCTION Two-phase hard/soft nanocomposite nanostructured magnetic materials are combinations of a highly coercive and moderate spontaneous magnetization hard phase and a high spontaneous magnetization soft phase. According to the Kneller-Hawig theory [1], by the exchange interaction between two nanostructured magnetic phases, the soft phase is hardened in the region contiguous to the hard phase leading to the energy product (BH)max improvement in comparison with that of the single hard phase. Several theoretical calculations showed that the energy product can reach 120 MGOe (1000 kJ/m3) with the presence of very high soft phase content ~ 90 vol.% [2, 3]. Therefore, the nanocomposite nanostructured magnetic materials have been under intensive investigation during the