PENGUKURAN MAGNETORESISTANCE PADA POLIETHYLEN GLICOL (PEG)-COATED NANOPARTIKEL MAGNETITE (Fe3O4) DAN BIOMOLEKUL DENGAN SENSOR THIN FILM GIANTMAGNETORESISTANCE (GMR)

Alfrie Musa Rampengan, Dr. Edi Suharyadi, M.Eng.

2013 | Tesis | S2 Ilmu Fisika

Telah dilakukan pengukuran magnetoresistance (MR) pada poliethylen glicol (PEG)-coated nanopartikel magnetik (Fe3O4) dan biomolekul formalin berbasis sensor film tipis Giant Magnetoresistance (GMR) yang berstruktur spin-valve Co90Fe19B4/Cu/Co90Fe19/Mn80Ir20 menggunakan System Four Point Probe Method (SFPPM). Sifat-sifat GMR yang dihasilkan dipengaruhi oleh ketebalan lapisan film dan respon spin-spin magnetiknya. Pengukuran MR pada range medan eksternal sekitar (0-75) gauss. Untuk ketebalan free layer CoFeB 10 nm dan barrier Cu 2,8 nm diperoleh perubahan range resistansi (17,0-12,0) Ω. Sedangkan pada ketebalan free layer CoFeB 7 nm dan ketebalan barrier Cu 2,2 nm diperoleh perubahan range resistansi (37,0-31,0) Ω. Perbedaan range pada kedua struktur GMR tersebut disebabkan oleh perbedaan ketebalan free layer CoFeB dan barrier Cu. Ketika dilapisi material magnetik nanopartikel Fe3O4, dilapisi oleh material magnetik nanopartikel Fe3O4 yang telah termodifikasi dengan polimer PEG-4000, maupun dilapisi oleh material magnetik nanopartikel Fe3O4 termodifikasi dengan PEG-4000 yang telah terikat dengan biomolekul formalin, terjadi perubahan sifat GMR yang ditunjukkan dengan perubahan nilai resistansi. Hal ini menunjukkan GMR sebagai sensor magnetik mampu untuk mendeteksi perilaku spin-spin magnetik material nanopartikel Fe3O4 tersebut.

The measurements of magnetoresistance (MR) on polyethylene glycol (PEG)- coated magnetite (Fe3O4) nanoparticles and formalin biomolecules using Giant Magnetoresistance (GMR) thin film sensor with a spin-valve structure of Co90Fe19B4/Cu/Co90Fe19/Mn80Ir20 were carried out by the System Four Point Probe Method (SFPPM). The properties of resultant GMR were strongly affected by the thickness of thin films and the responses of magnetic spins. The measurements of MR at a range of external range were approximately (0-75) gauss. For the thicknesses of 10 nm CoFeB free layer and 2.8 nm Cu barrier, it is found that changes in resistance were (17.0 to 12.0) Ω, while for those of 7 nm CoFeB free layer and of 2.2 nm Cu barrier, the changes in resistance were (37.0- 31.0) Ω. Difference in range of the two GMR structures was caused by difference in thickness of CoFeB free layer and Cu barrier. When it was coated by the magnetite materials of Fe3O4 nanoparticles, those modified by PEG-4000 polymer, and those modified by PEG-4000 polymer that was bonded with formalin biomolecule, change in GMR properties occurred, which was indicated by change in resistance value. It shows that GMR as the magnetite sensor was able to detect behavior of the magnetic spins of Fe3O4 nanoparticles.

Kata Kunci : Magnetoresistance, Giant-Magnetoresistance, Nanopartikel Fe3O4, Poliethylen-glicol 4000