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Yohanes Edi Gunanto
Sintesis dan karakterisasi La1-xCaxMn1-yCuyO3 sebagai bahan giant magnetoresistance dengan berbagai variasi x dan y = Synthesis and characterization La1-xCaxMn1-yCuyO3 as a matter giant magnetoresistence with the variation x and y
"ABSTRAK
Thesis ini menyajikan hasil penelitian eksperimen tentang struktur, besaran magnet, specific heat dan giant magnetoresistance dari sampel polikristal manganat tanah jarang seri LaI-XCaxMni-yCuyO3 dengan x = 0,1 ; 0,47 dan 0,73 dan 0 < y < 0,l9. Sampel disiapkan dengan metode reaksi zat padat. Analisis struktur menggunakan difraksi sinar-x dan high resolution powder diffraction (HRPD) dengan program fullprof. Semua sampel mempunyai struktur orthorhombic dengan space group Pnma. Pada suhu kamar semua sampel bersifat paramagnetik dan berubah campuran antara antiferromagnetik (AFM) dengan ferromagnetik (FM) pada suhu rendah dan juga akibat adanya medan magnet luar. Pendopingan Cu pada posisi Mn mengakibatkan menurunnya momen magnet pg. Besaran specific heat pada suhu rendah didominasi oleh faktor charge carriers (70, sedangkan faktor kisi B kcnstan, sementara faktor spin wave-nya diabaikan. Sifat giant magnetoresistance (GMR) pads suhu ruang menunjukkan bahwa pendopingan Cu pada Mn mengakibatkan menurunnya nilai magnetoresistansinya. Semakin tinggi nilai medan magnet luar, maka nilai magnetoresistensinya juga semakin naik.
ABSTRACT
This thesis presents result of an experimental study on structure, magnetic properties, specific heat and giant magnetoresistance of polychrystal samples manganese rare-earth series LaI-XCaxMni-yCuyO3 with x = 0.1; 0.5, and 0.9 and y = 0; 0.05; 0.l0; 0.15, and 0.20. All samples by solid state reaction. The structure analysis use x-ray diffraction and high resolution powder diffraction with fullprof program. The structure of all samples are orthorhombic with space group Pnma. At room temperature all samples are paramagnetic and change became ferromagnetic at low temperature and consecuence external magnetic field too. The doping Cu at Mn site makes decrease the moment magnetic. The specific heat at low temperature, upon increasing the Cu dopant, the y and therefore the charge carriers increase. The specific heat for all samples are insensitive to the external magnetic field up to 9 T. The presence of external magnetic field has no influence on the p value for samples with and without Cu dopant. At room temperature, the doping of Cu at Mn makes decrease the magnetoresistance. The increasing external magnetic field, the magnetoresistance are increasing to."
Depok: 2009
D1241
UI - Disertasi Open  Universitas Indonesia Library
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Yohanes Edi Gunanto
Phase transitions in La0.73Ca0.27Mn1-xCuxO3 (0 < X < 0.19)
"We have performed
resistivity measurements as a function
of temperature, with and without
an external magnetic field. Magnetization measurements are also done as a function of
temperature M(T) as
well as a function of an external magnetic field M(H) for La0.73Ca0.27Mn1-xCuxO3compounds with 0
The samples with x = 0 and 0.06 are insulators. As for
the samples with x =
0.10, 0.13, and
0.19, they undergo an insulator to metal
transition as the temperature is lowered. The insulator-metal transition temperatures
are 24 K, 74 K, and 69 K for x =
0.10, 0.13, and
0.19, respectively. The magnetoresistance decreases with increasing values of Cu, i.e. 75%, 72%, 64%, and 35% for x = 0, 0.06, 0.10, and 0.13
respectively. Samples in accordance
with the model of crystalline metal Ln R
vs. 1/T are compared to Mott insulator models Ln R vs. 1/T0.25. Based on the magnetization curve, a
paramagnetic to ferromagnetic transition is observed at Curie temperature, TC,
of ~ 196 K, 170 K, 140 K, 137 K, and 113 K for x = 0, 0.06, 0.10, 0.13, and 0.19 respectively."
2017
J-Pdf
Artikel Jurnal  Universitas Indonesia Library