Kontan Tarigan | Mercu Buana University (original) (raw)

Papers by Kontan Tarigan

Journal of Magnetism and Magnetic Materials, 1997

... Thus the effect of annealing in the center of the Fe layers, is to increase the thickness of ... more ... Thus the effect of annealing in the center of the Fe layers, is to increase the thickness of pure amorphous iron which is non-magnetic at room temperature, and so decreases (Blaf). A. Fnidiki et al. ... The layers begin to mix, increasing the thick-ness of the interfaces. ...

Journal of Physics: Conference Series, 2017

The structural and the magnetic properties of nanocrystalline Fe47.5Mn47.5C5 alloys were prepared... more The structural and the magnetic properties of nanocrystalline Fe47.5Mn47.5C5 alloys were prepared by using a mechanical alloying technique, used the commercial Fe, Mn, and C powders as precursors. It was studied in detail as function of the milling times of 1-to 48 hrs. The structural analysis based on X-ray diffraction and extended X-ray absorption fine structure spectroscopy revealed that the alloying process took place after 36 hrs milling. Concerning the magnetic behavior, the data obtained from a vibrating sample magnetometer showed that both the magnetic saturation and the coercivity depended strongly on the milling time and the crystallite size. With these results, by adjusting the milling time shows that an appropriate structural transformation and appropriate magnetization value.

IEEE Transactions on Magnetics, 2009

ABSTRACT Fe55Mn10Al35 alloys were prepared by mechanical alloying. Local ordering around the cent... more ABSTRACT Fe55Mn10Al35 alloys were prepared by mechanical alloying. Local ordering around the central atom was examined with milling time by using extended X-ray absorption fine structure. The structural and magnetic evolution was analyzed by EXAFS and Mossbauer study as a function of milling time. The first shell of the Fourier transformed spectra changed with milling time, indicating a change in the local ordering around the central Fe atom. X-ray diffraction patterns indicate a bcc phase after 24 h milling time. For 1 h milled sample, Mossbauer spectra analysed three sextets as bcc-Fe phase, broad sextet and Fe surrounded Al and Mn phase. The magnetization showed decrease with milling time corresponding to magnetic dilution.

Journal of the Korean Physical Society, 2010

ABSTRACT The structural and the magnetic properties of nanocrystalline Fe50Al50 alloys prepared b... more ABSTRACT The structural and the magnetic properties of nanocrystalline Fe50Al50 alloys prepared by using a mechanical alloying process (using commercial Fe and Al powders as precursors) were studied in detail as functions of the milling time for milling times ranging from 1 hr to 24 hrs. The structural analyses based on X-ray diffraction (XRD) and extended X-ray absorption fine structure spectroscopy (EXAFS) revealed that the alloying process took place after 12 hrs of milling. Using the Williamson-Hall plot, we found that the crystallite size decreased from to 220 to 14.3 nm while the strain increased from 5.32 x 10(-3) to 19 x 10(-3) when the milling time was varied from 1 hr to 24 hrs. Concerning the magnetic behavior, the data obtained from a superconducting quantum interference device (SQUID) showed that both the magnetic saturation (M-s) and the coercivity (H-c) depended strongly on the milling time and that these dependence were related to changes in the crystallite size. With these results, we believe that by adjusting the milling time, we can obtain an appropriate structural transformation and appropriate magnetization values.

Journal of Magnetism and Magnetic Materials, 2015

We investigated magnetic properties of La 0.7 Ca 0.3 Mn 1-x Fe x O 3 (x = 0.09 and 0.11) compound... more We investigated magnetic properties of La 0.7 Ca 0.3 Mn 1-x Fe x O 3 (x = 0.09 and 0.11) compounds in terms of isothermal magnetization analysis and scaling behavior with various critical exponents. From the Landau theory of magnetic phase transition, we found that the paramagnetic to ferromagnetic phase transition in La 0.7 Ca 0.3 Mn 1-x Fe x O 3 (x = 0.09 and 0.11) compounds is the type of second order magnetic transition (SOMT), which contrary to the first order magnetic transition (FOMT) for low Fe-doped compounds (x < 0.09) in previous reports. When we investigate the critical behavior of the compounds near T = T c by the modified Arrott plot, Kouvel-Fisher plots, and critical isothermal analysis, the estimated critical exponent β, γ, δ are in between the theoretically predicted values for three-dimensional Heisenberg and meanfield interaction models. It is noteworthy that the scaling relations are obeyed in terms of renormalization magnetization m=ε-β M(H,ε) and renormalized field h =|ε| β+γ H. Temperaturedependent effective exponents β eff and γ eff correspond to the ones of disordered ferromagnets. It is shown that the magnetic state of the compounds is not fully described by the conventional localized-spin interaction model because the ferromagnetic interaction has itinerant character by increasing Fe-doping concentration.

Journal of Magnetism and Magnetic Materials, 2017

We used the mechanical milling to prepare orthorhombic Sm 0.12 Ca 0.88 MnO 3 samples with the ave... more We used the mechanical milling to prepare orthorhombic Sm 0.12 Ca 0.88 MnO 3 samples with the average crystallite size (d) changing from 100 to 139 nm. Their magnetic and magnetocaloric properties were then studied upon magnetization data versus the temperature and magnetic field, M(T, H). The results revealed the samples undergoing the ferromagnetic-paramagnetic (FM-PM) phase transition at the Curie temperature T C  110 K. Around this transition, the magnetic-entropy change (S m) reaches the maxima. The maximum |S m | values are about 2-4 Jkg-1 K-1 , corresponding to relative cooling power of 35~60 Jkg-1 , for an applied field H = 30 kOe. The assessments based on Banerjee's criteria and constructing a universal curve for |S m (T, H)| data indicate the samples having the nature of a second-order phase transition. Also, the detailed analyses based on the Curie-Weiss law and magnetic-order exponent prove the existence of the Griffiths phase and magnetic inhomogeneity in the samples. These properties would be changed by changing d.

Journal of the Korean Physical Society, 2013

ABSTRACT Nanocrystalline Fe90−x Mn10Alx (x = 10, 20, 30, and 40) were prepared via mechanical all... more ABSTRACT Nanocrystalline Fe90−x Mn10Alx (x = 10, 20, 30, and 40) were prepared via mechanical alloying by using Fe, Mn, and Al powders with a 48 hours milling time. The structural and the magnetic properties were studied. All X-ray diffraction peaks are broader and shifted to smaller angle with increasing Al contents, depending on the crystalline size and the lattice parameter. All the samples exhibit alloys behavior with an average crystallite size around 10 nm. The magnetic saturation, coercivity, and permeability obtained from measurements using a vibrating sample magnetometer showed strong dependences on the Al content and these dependences were related to changes in the structure and the crystallite size. The hyperfine field obtained from Mössbauer spectroscopy varied with the Fe content. These results suggest that, by adjusting Al, appropriate magnetization values can be obtained without affecting the coercivity and the structure of the bcc phase.

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IEEE Transactions on Magnetics, 2010

Advanced Materials Research, 2011

The structural and the magnetic properties of nanocrystalline and amorphous Fe55Mn10Al35 alloys p... more The structural and the magnetic properties of nanocrystalline and amorphous Fe55Mn10Al35 alloys prepared by the mechanical alloying process are studied as functions of the milling time varying from 1 hr to 48 hrs. Structural analyses based on X-ray diffraction (XRD) and extended X-ray absorption fine structure spectroscopy (EXAFS) reveal that the alloying process took place after 12-hr milling. Nanocrystalline alloys are found until 24-hrs milling, and an amorphous phase afterward. Concerning the magnetic behavior, the data obtained from a vibrating sample magnetometer show that both the magnetization saturation (Ms) and the coercivity (Hc) are dependent strongly on the milling time and the crystallite size. By adjusting the milling time, both appropriate structural transformation and magnetization values are obtained.

Local structural and magnetic characterization of (Ni0.5Al0.5)100-xCx (x = 0, 10, 30, and 50 at. ... more Local structural and magnetic characterization of (Ni0.5Al0.5)100-xCx (x = 0, 10, 30, and 50 at. %) nanocrystalline alloys which were prepared by mechanical alloying (MA) technique at 12 hrs milling time, have been carried out in detail. The nanocrystalline size and shape were examined using scanning electron microscopy (SEM). The effect of carbon on structural properties has been investigated using x-ray diffractometer (XRD) and extended x-ray absorption fi ne structure spectroscopy (EXAFS), whereas magnetic properties was examined by vibrating sample magnetometer (VSM). All the samples revealed nanocrystalline alloys. The maximum magnetic saturation (Ms) at about 0.7 emu/g and the minimum coercivity (Hc) at about 135 Oe would be found for 10% carbon content.

Fe50Mn50 nano-crystalline alloys are prepared by the mechanical alloying process as a function of... more Fe50Mn50 nano-crystalline alloys are prepared by the mechanical alloying process as a function of milling time. The effect of milling time on structural properties has been investigated by using XRD and EXAFS, which confirmed the alloy after 12 hours. The particle size and shape are examined by using SEM. Magnetic properties are examined by using SQUID. Magnetic saturation is decreased due to resulting magnetic dilution and decreasing particles size, and also the coercivity is decreased due to growing single-domain status as the particles size is reduced. Fe–Mn alloys have been extensively studied for magnetic thin-film device applications. A FeMn thin antiferromagnetic layer has been used to enhance the function of a spin-valve read sensor. The antiparallel alignment of Mn magnetic moment has been observed frequently in magnetic materials. Superparamagnetic behavior has been observed in FexMn1–x ultra thin film. Also, various phenomena such as spin transition and shape-memory effec...

Magnetic properties of nanocrystalline Fe50Al50 alloys prepared by mechanical alloying technique ... more Magnetic properties of nanocrystalline Fe50Al50 alloys prepared by mechanical alloying technique (using commercial Fe and Al powders as precursors) were studied in detail as a functions of the milling time ranging from 1 to 24 hrs. The structural analyses based on X-ray diffraction (XRD) and extended X-ray absorption fi ne structure spectroscopy (EXAFS) revealed that the alloying process took place after 12 hrs of milling time. Concerning the magnetic behavior, the data that were obtained from a superconducting quantum interference device (SQUID) showed that both the magnetic saturation (Ms) and the coercivity (Hc) depend strongly on the milling time. From the results that we obtain, we found out that by adjusting the milling time, is a key factor in obtaining an appropriate structural transformation and appropriate magnetization values.

한국자기학회 2007년도 정기총회 동계학술연구발표회 및 스핀트로닉스와 나노물리에 관한 국제심포지움, Dec 1, 2007