日本応用磁気学会誌

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The present paper concerns the effects of a static magnetic field on the freezing of cattle sperm collected from four bulls. Semen samples were exposed for 30 minutes to a magnetic field of 600 Gauss (G) at 4°C and enclosed in plastic semen straws. Other samples were exposed to a magnetic field while enclosed in semen straws with a 1,250 G magnetic grain at 4°C. Straw samples were frozen in the liquid nitrogen and thawed in a water bath at 38°C. These thawed semen samples were incubated in vitro at 38°C. A solution of 2% Eosin Bluish was used to determine the viability of the sperm, and the CellSoft sperm motion analysis system was used to determine the motility and velocity of the sperm at thawing, after 1 hour, and after 3 hours. The viability and motility of the sperm exposed to the magnetic field for 30 minutes were higher than non-exposed sperm. No deformed calves born as a result of the artificial insemination of frozen-thawed sperm exposed to a magnetic field of 600 G for 30 minutes.

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The thermomagnetization curves of rapidly quenched Ni_1-xMn_x (x=0.20, 0.21, 0.23, 0.25, 0.27) alloys and Ni_0.79Mn_0.21 alloy annealed at 693 K for 200 h and 1,000 h were investigated in the temperature range of 100-650 K. The change in saturation magnetization and Curie temperature with heat treatment and Mn concentration was studied on the basis of the atomic short-range order estimated by statistical and EXAFS methods. The magnetism of these alloys depends on the number of nearest-neighbor Mn atoms around an Mn atom. After annealing for 1,000 h, the thermomagnetization curve of Ni_0.79Mn_0.21 alloy shows a double stage, which consists of the ferromagnetic phase and a long tail above the Curie temperature. The latter was analyzed by using a superparamagnetic model as a random set of ferromagnetic clusters distributed in a nonmagnetic matrix.

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