Detection of Neodymium-Rich Phase for Development of Coercivity in Neodymium-Iron-Boron-Based Alloys with Submicron-Sized Grains Using Positron Lifetime Spectroscopy

In order to evaluate the relationship between positron lifetime and microstructure, which contributes to the development of coercivity in hydrogenation-disproportionation-desorption-recombination (HDDR)-processed Nd-Fe-B-based alloys, detailed studies of positron lifetime spectroscopy were performed on HDDR-processed Nd-Fe-B-based alloys during desorption-recombination (DR) treatment. After the onset of coercivity, the change in positron lifetime closely corresponded to the change in intrinsic coercivity (H cJ ) with the progress of DR treatment. This result can be explained in terms of the grain size of the recombined Nd 2 Fe 14 B phases and the diffusion length of positrons, which annihilate in the matrix before reaching the grain boundary. Furthermore, positron lifetime spectroscopy was able to detect small changes in the grain boundary region very sensitively compared with thermal desorption spectroscopy (TDS) and X-ray diffraction (XRD). These changes in the grain boundary region caused the onset of coercivity attributed to the formation of Nd-rich intergranular phases. These results indicate that formation of a small amount of the Nd-rich intergranular phase during the DR process, which could be detected by positron lifetime spectroscopy, contributes to the onset of coercivity, even if NdH x phases remain

内因性プロゲステロン分泌は、合成プロゲステロン製剤を用いたホルモン補充凍結胚移植周期において妊娠予後予測因子になり得る

Purpose: A retrospective, cohort study was conducted between 2009 and 2017 in a private infertility center to determine the predictive value of endogenous estrogen (E2) and progesterone (P4) levels in hormone‐replacement frozen embryo replacement (FER) treatment cycles. Methods: A total of 120 consecutive, infertile patients who became pregnant after FER cycles were analyzed (age: 37.4 ± 4.4 years). Electively vitrified blastocysts were created during natural cycle IVF or mild ovarian stimulation treatments and subsequently transferred through delayed vitrified‐thawed blastocyst transfer cycles supplemented with estrogens and a combination of synthetic progestogens. Serum E2 and progesterone P4 levels were intensively monitored every five days (from the day after embryo transfer until 9w1d of pregnancy) and compared among patients with a subsequent live birth (n = 76) or first‐trimester pregnancy loss (n = 44). Results: Endogenous placental activity started as early as 5‐6th pregnancy week differing significantly according to pregnancy outcome. For P4, the exponential rise from 6w2d onwards allowed distinguishing between failing and successful conceptions. For P4, lower quartiles of the live birth group did not intersect with upper quartiles of the miscarriage group. Conclusions: Innovative FER protocols incorporating synthetic progestogens allow the correct measurement of endogenous placental activity and could help to monitor early first‐trimester ART pregnancies

Realization of a scanning soft X-ray microscope for magnetic imaging under high magnetic fields

For the purpose of imaging element- and shell-specific magnetic distributions under high magnetic fields, a scanning soft X-ray microscope has been developed at beamline BL25SU, SPring-8, Japan. The scanning X-ray microscope utilizes total electron yield detection of absorbed circularly polarized soft X-rays in order to observe magnetic domains through the X-ray magnetic circular dichroism effect. Crucially, this system is equipped with an 8 T superconducting magnet. The performance and features of the present system are demonstrated by magnetic domain observations of the fractured surface of a Nd₁₄.₀Fe₇₉.₇Cu₀.₁B₆.₂ sintered magnet.Y.Kotani, Y.Senba, K.Toyoki, et al. Realization of a scanning soft X-ray microscope for magnetic imaging under high magnetic fields. Journal of Synchrotron Radiation 25, 1444 (2018); https://doi.org/10.1107/S1600577518009177

Magnetotransport through the spin-reorientation transition in Tm2Fe14B

The electrical resistivity and Hall effect for a single crystal of Tm2Fe14B have been measured over the range of temperature (T) from 4 to 600 K in magnetic fields of up to 5 T. The resistivity exhibits a small step-like rise at the spin-reorientation temperature Ts, which is 311 K, and a broad minimum at 535 K. In addition, the Hall coefficient shows an anomaly at Ts, and drops sharply as T approaches the Curie temperature (549 K) from below. The lower-temperature anomalies, both in the resistivity and in the Hall coefficient, show that the spin-reorientation transition in Tm2Fe14B is of first order. The high-temperature Hall anomaly is probably produced by critical spin fluctuations near the Curie point. Dominant scattering mechanisms that underlie the Hall effect and magnetoresistance in Tm2Fe14B are inferred.This work was supported by Project MAT 99/1142 of Comision Interministerial de Ciencia y Tecnologia (CICYT).Peer reviewe