Yazar "Ak, Fermin" seçeneğine göre listele

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    Key role of central antimony in magnetization of Ni 0.5 Co 1.5 MnSb quaternary Heusler alloy revealed by comparison between theory and experiment
    (Elsevier, 2019) Şarlı, Numan; Ak, Fermin; Özdemir, Evren Görkem; Saatçi, Buket; Merdan, Ziya
    Temperature dependent magnetization of Ni0.5Co1.5MnSb quaternary Heusler alloy is investigated both theoretically (m-T) and experimentally (M-T). According to the XRD data, the crystal structure of Ni0.5Co1.5MnSb is compatible with the cubic crystal structure with space group symmetry Fm-3m and the lattice parameter of a?=?5.968?Å. Experimental M-T curve is obtained at H?=?1?T. The Curie temperature is obtained at about TCEXP?=?538.3?K. We also use effective field theory (EFT) developed by Kaneyoshi to model and investigate the m-T properties of Ni0.5Co1.5MnSb. We find that the theoretical m-T and experimental M-T results overlap at low temperatures (T??100?K). In particular, the theoretical mSb3-T curve of the central Sb3 atom is much closer to the experimental M-T curve of Ni0.5Co1.5MnSb than that of the other components (mMn1, mMn2, mMn3, mSb1, mSb2, mNi and mCo). Therefore, we strongly propose that one needs to pay close attention to the magnetization of the central atom especially in the lattice of Heusler alloys in both their predictive and experimental studies.
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    Structural and magnetic characterisation of Co substituted Ni2MnSb Heusler alloy: effect of cobalt substitution on magnetism and Curie temperature
    (Taylor and Francis Ltd., 2021) Öz, Erdinç; Ak, Fermin; Saatci, Buket
    In this study, Ni2-xCo x MnSb full-Heusler alloys (1.00 ? x ? 1.75) were prepared by arc melting process, and examined by X-ray diffraction (XRD), scanning electron microscopy (SEM), and SQUID. The L21 crystal structure of the synthesised Heusler alloy was confirmed by XRD patterns, and it was observed that the use of Co instead of Ni caused a decrease in the interatomic distance. The magnetisation results revealed that all samples show ferromagnetic (FM) behaviour, and substitution Co for Ni leads to increasing FM interactions in the samples. The calculated magnetic moment per formula unit increase from 4.38 µB(x =1) to 5.17 µB (x =1.75). On the other hand, the increase in FM interaction caused an increase in ferromagnetic-paramagnetic (PM) phase transition (T C) temperatures from 513 (x =1) to 568 K (x =1.75). The ability to control the Curie temperature with Co substitution makes these alloys suitable candidates for future spintronics and magnetoelectronic applications.
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    Structural and magnetic properties of Ni2-xCoxMnSb (x: 0.00, 0.25, 0.50 and 1.00) Heusler alloys: The relationship between Curie temperature and lattice parameter
    (Elsevier, 2019) Ak, Fermin; Öz, Erdinç; Saatçi, Buket
    Ni2-xCoxMnSb Heusler alloys were fabricated by arc melting process. The endothermic/exothermic reactions with increasing temperature were determined by DTA analysis and it was found that the chancing Co concentration in the system causes the change in the reaction temperatures. The temperature dependence of the magnetization from base temperature to 600?K, a crucial value for the Curie temperature, and lattice parameters of the samples were determined. It was suggested that increasing Co in the samples causes the change of the grain formation and the increasing Co concentration in the system also causes the change of the Curie temperature values with decreased the lattice parameters.