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Longitudinal and Polar MOKE Magnetometry of
Magnetoresistive Cobalt
Thin Films Prepared by Thermal Evaporation
(Magnetometri
Longitudal dan Kutub MOKE Filem Nipis Kobalt Magnetorintangan yangdisediakan
Melalui Penyejatan Terma)
C. Sirisathitkul*
Magnet Laboratory, School of Science, Walailak
University, Nakhon Si Thammarat
80161 Thailand
Y. Pansong
Center of Scientific and Technological
Equipment, Walailak University
Nakhon Si Thammarat , 80161 Thailand
S. Rattanasuporn
Beamline Division, Synchrotron Light
Research Institute, Nakhon Ratchasima
30000 Thailand
Received: 3 August 2011 / Accepted: 27
October 2011
ABSTRACT
Cobalt films of thickness 21, 29 and 68
nm were prepared by thermal evaporation with a deposition rate around 0.3 nm/s.
Their hysteresis loops from longitudinal and polar magneto-optic Kerr effect (MOKE)
magnetometry differed from typical characteristics of uniaxial magnetic
anisotropy but still indicated the preference of in-plane anisotropy over
perpendicular anisotropy. The longitudinal hysteresis loop of the 68 nm-thick
film was decidedly in a transcritical state signified by an enhanced coercive
field. Changing the angle (θ) between the 2500 Oe-magnetic field and the
current gave rise to the change in electrical resistance (Rθ) of 29
nm-thick film and the plot between Rθ and cos2θ
could be linearly fitted. The changes in resistance due to this anisotropic
magnetoresistance (AMR) effect ranged from
-0.08 % (θ = 90º) to +0.04 % (θ = 0º).
Keywords: Anisotropic magnetoresistance;
ferromagnetic thin film; hysteresis loop; magneto-optic Kerr effect; thermal
evaporation
ABSTRAK
Filem kobalt dengan ketebalan 21,29 dan 68
nm telah disediakan melalui penyejatan terma dengan kadar pemendapan 0.3nm/s. Gelung
histerisis daripada magnetometri longitudal dan kesan magneto-optik Kerr adalah
berbeza daripada ciri-ciri biasa anisotrop magnet ekapaksi tetapi masih menunjukkan
kecenderungnan kepada anisotrop dalam-satah berbanding anisotropy serenjang.
Gelung histerisis longitudal filem dengan ketebalan 68 nm jelas dalam keadaan
transkritikal dan ditandakan oleh medan paksaan yang meningkat. Mengubah sudut
(θ) antara medan magnet 2500 Oe dan arus telah mengubah rintangan elektrik
(Rθ) filem dengan ketebalan 29 nm dan plot antara Rθ dan cos2θ boleh disuaikan secara linear. Perubahan dalam
rintangan disebabkan oleh magnetorintangan tak isotropik (AMR) ini adalah
daripada -0.08% (θ=90o) ke 0.04% (θ= 0o).
Kata
kunci: Filem nipis feromagnet; gelung histerisis; kesan magneto-optik Kerr;
magnetorintangan anisotropik; penyejatanterma
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*Corresponding
author; email: schitnar@wu.ac.th
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