tailieunhanh - Molecular-field Study on Sn Substituted Yttrium Iron Garnet

Samples with the compositions and were prepared by using a sol-gel technique. The influence of the substituted non-magnetic cations with different valences in the structural and magnetic properties was studied. X-ray diffraction and fieldemission electron scanning microscope techniques were used to study the crystal structure and morphology. | VNU Journal of Science: Mathematics – Physics, Vol. 34, No. 1 (2018) 67-74 Molecular-field Study on Sn Substituted Yttrium Iron Garnet Nguyen Phuc Duong* ITIMS, Hanoi University of Science and Technology, No. 1, Dai Co Viet, Hai Ba Trung, Hanoi, Viet Nam Received 31 January 2018 Revised 28 February 2018; Accepted 28 February 2018 Abstract: Samples with the compositions and were prepared by using a sol-gel technique. The influence of the substituted non-magnetic cations with different valences in the structural and magnetic properties was studied. X-ray diffraction and fieldemission electron scanning microscope techniques were used to study the crystal structure and morphology. Magnetization curves in fields up to 10 kOe and in temperature range from 80 K to 570 K were measured by means of a vibrating sample magnetometer. Saturation magnetization as a function of temperature of the two samples was analyzed based on the molecular-field theory from that models for site occupancy and valence states of cations in the crystal structures were derived. Keywords: Yttrium iron garnet; Ca and Sn substitution; magnetization; Curie temperature; molecular-field calculation 1. Introduction Yttrium iron garnet (YIG) crystallizes in cubic structure with the space group Ia3d. Y3+ ions occupy the dodecahedral sites 24c while Fe3+ ions are distributed over the octahedral sites 16a and tetrahedral sites 24d forming two magnetic sublattices [a] and (d), respectively. Stoichiometric YIG is a good insulator with room temperature resistivity greater than 1012 Ωcm [1] and has been widely used in high frequency applications [2]. By doping or substituting cations which have valences other than 3, charge carriers may arise in the materials and n- or p-type conductivity can be obtained. Donor or acceptor centers are created by substituting cations with valence greater (., Si4+, Ge4+, Sn4+, Zr4+, Sb5+, Mo6+ etc.) and less (Ca2+, Pb2+, Zn2+, Mg2+ .