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A 57 Fe nucleus in the solar core could emit a 14.4-keV monochromatic axion through the M1 transition if a hypothetical elementary particle, axion, exists to solve the strong CP problem. Transition edge sensor (TES) X-ray microcalorimeters can detect such axions very efficiently if they are again converted into photons by a 57 Fe absorber. We have designed and produced a dedicated TES array with 57 Fe absorbers for the solar axion search. The iron absorber is set next to the TES, keeping a certain distance to reduce the iron-magnetization effect on the spectroscopic performance. A gold thermal transfer strap connects them. A sample pixel irradiated from a 55 Fe source detected 698 pulses. In contrast to thermal simulations, we consider that the pulses include either events produced in an iron absorber or gold strap at a fraction dependent on the absorption rate of each material. Furthermore, photons deposited on the iron absorber are detected through the strap as intended. The identification of all events still needs to be completed. However, we successfully operated the TES with the unique design under iron magnetization for the first time. [ABSTRACT FROM AUTHOR]

Abstract: Magnetic thermal expansions of itinerant electron antiferromagnets are discussed along the Grüneisen''s approach to the thermal expansions due to lattice vibrations. We show that the thermal expansion consists of two terms, , that corresponds to the Moriya–Usami''s result, and a new term derived for ferromagnets recently. Comparison of these terms shows that the second term becomes dominant at low temperatures around the magnetic instability point, leading to the -linear behavior there for nearly antiferromagnetic compounds. [Copyright &y& Elsevier]