Sains Malaysiana 37(2): 205-210(2008)
Microwave, Magnetic, Dielectric and Absorption Properties
of Some Cerium-Yttrium Iron Garnets
(Sifat Mikrogelombang, Magnet Dielektrik dan Penyerapan
Beberapa Garnet besi Serium-Iterium)
Mustaffa Hj. Abdullah, Mardiana Ahmad, Noor Baa'yah Ibrahim & Ahmad Nazlim Yusoff
Physics Programme, School of Applied Physics, Faculty of Science and Technology
Universiti Kebangsaan Malaysia, 43600 UKM Bangi, Selangor D.E. Malaysia
Diserahkan : 30 Mei 2007 / Diterima: 24 Oktober 2007
ABSTRACT
This paper describes the microwave properties and application of some cerium-substituted yttrium-cerium iron garnets, Y3-xCexFe5O12 (x £ 0.15), as microwave absorbing materials. The complex scattering parameters due to reflection (S11* and S22*) and transmission (S21* and S12*), relative dielectric permittivity (er* = er¢ - jer¢¢) and relative magnetic permeability (mr* = mr¢ - jmr¢¢) were measured using a microwave vector network analyzer by means of a coaxial two-port technique in the frequency range of 0.30 – 13.51 GHz. The microwave power absorption in the materials is discussed as due to the dielectric and magnetic losses. The dielectric losses are interpreted as due to orientational dielectric relaxation and direct current conductivity. The maxima in magnetic losses correspond to domain wall and internal or natural ferromagnetic resonances. Microwave absorbing properties based on a metal-backed absorber were studied and discussed.
Keywords: Yttrium iron garnet; Magnetic permeability; Dielectic permittivity; Microwave; Absorption
ABSTRAK
Kertas ini memperihalkan sifat mikrogelombang dan kegunaan beberapa garnet besi cerium - itrium berganti cerium, CexY3-xFe5O12 (x £ 0.15), sebagai bahan penyerap mikrogelombang. Parameter penyerakan kompleks daripada pemantulan, (S11* and S22*), dan penghantaran, (S21* and S12*), ketelusan dielektrik relatif (er* = er¢ - jer¢¢) dan kebolehtelapan magnet relatif (mr* = mr¢ - jmr¢¢) diukur dengan sebuah penganalis rangkaian mikrogelombang vektor melalui teknik sepaksi dua-port dalam julat frekuensi 0.30-13.51 GHz. Penyerapan mikrogelombang di dalam bahan dibincangkan sebagai disebabkan oleh kehilangan dielektrik dan magnet. Kehilangan dielektrik ditafsirkan berpunca daripada relaksasi dielektrik orientasi dan kekonduksian arus terus. Keadaan maksimum dalam kehilangan magnet disebabkan oleh resonans dinding domain dan ferimagnet dalaman atau semulajadi. Sifat penyerapan mikrogelombang yang berdasarkan suatu penyerap berlapikkan logam dikaji dan dibincangkan.
Kata kunci: Garnet itrium besi; Kebolehtelapan magnet; Ketelusan dielektrik; Penyerapan mikrogelombang
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