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,  Y_3-xCe_xFe₅O₁₂   (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   (e_r* = e_r¢ - je_r¢¢)  and  relative  magnetic  permeability (m_r* = m_r¢ - jm_r¢¢) 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,  Ce_xY_3-xFe₅O₁₂   (x  £ 0.15),  sebagai bahan penyerap mikrogelombang. Parameter penyerakan kompleks daripada pemantulan, (S₁₁* and S₂₂*),   dan penghantaran,  (S₂₁*  and  S₁₂*),  ketelusan dielektrik relatif (e_r* = e_r¢ - je_r¢¢)     dan kebolehtelapan magnet relatif (m_r* = m_r¢ - jm_r¢¢) 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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