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Wen Hu,
Kouichi Hayashi,
Tokujiro Yamamoto,
Naohisa Happo,
Shinya Hosokawa, Tomoyuki Terai,
Takashi Fukuda,
Tomoyuki Kakeshita,
Honglan Xie,
Tiqiao Xiao,
Motohiro Suzuki
Physical Review B (Condensed Matter and Materials Physics). 01/2009; 80(6):060202.
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ABSTRACT: We have examined magnetizations as a function of temperature and magnetic field in layered perovskite manganites La2−2xSr1+2xMn2O7 single crystals (x=0.313, 0.315, 0.318, 0.320 and 0.350) in order to determine the phase boundary between two ferromagnets (one is an uniaxial ferromagnet whose easy axis is parallel to the c-axis and the other is a planar ferromagnet whose easy axis is within the ab-plane) and following results are obtained: (i) all the present manganites exhibit magnetic transitions from a ferromagnet to a paramagnet at 76, 107, 116, 120 and 125 K for x=0.313, 0.315, 0.318, 0.320 and 0.350, respectively; (ii) for x=0.318, 0.320 and 0.350, the magnetic structure is a planar ferromagnet below Curie temperature; (iii) for x=0.313 and 0.315, the magnetic structure changes from an uniaxial to a planar ferromagnet at 66 and 85 K, respectively. From the results described above we have constructed the magnetic phase diagram of layered perovskite manganite La2−2xSr1+2xMn2O7 (0.313⩽x⩽0.350).
Journal of Magnetism and Magnetic Materials 303(1):138-141. · 1.78 Impact Factor
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ABSTRACT: X-ray fluorescence holography is a relatively new experimental method for the local three-dimensional atomic structure in an element-specific way. We measured the holograms of Ti50Ni44Fe6 single crystal at 100 and 225 K, which correspond to its commensurate and parent phases, respectively. The atomic images of both phases were successfully reconstructed. The difference of both images shows a possibility that a cluster structure around the Fe atoms forms with a radius of 8 Å in the commensurate phase.
Journal of Crystal Growth.
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Wen Hu,
Kouichi Hayashi,
Tokujiro Yamamoto,
Naohisa Happo,
Shinya Hosokawa, Tomoyuki Terai,
Takashi Fukuda,
Tomoyuki Kakeshita,
Honglan Xie,
Tiqiao Xiao,
Motohiro Suzuki
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ABSTRACT: The phase transition behavior of the local structure around Fe in a shape-memory-alloy-related material, Ti50Ni44Fe6, was evaluated by x-ray fluorescence holography. The Fe Kα holograms were recorded at 225 and 100 K, which correspond to the parent and commensurate phases, respectively. The atomic images at both the phases show that the first neighbor Ti atoms around Fe, fluctuating in the parent phase, is strongly stabilized in the commensurate phase and that a clusterlike structure with a radius of 8 Å is formed in this lower temperature phase. These dynamically structural changes offer important keys to understanding the precursors to the martensite phase transition of the TiNi series.
Phys. Rev. B. 80(6).
