溶融YBa_2Cu_3O_yの交流磁化応答における微弱直流磁場印加効果 Effect of Weak DC Magnetic Fields on the AC Magnetization of a Melt-Processed YBa_2Cu_3O_y
We studied, both theoretically and experimentally, the ac magnetic response of type-II superconductors superimposed on a weak H<SUB>dc</SUB> field. Theoretical simulations were made within the construct of the Kim-Anderson critical-state model, where the critical current density J<SUB>c</SUB> is assumed to be given by J<SUB>c</SUB>=k/(Bo+|Bi|). k and B<SUB>o</SUB> are temperature-dependent material parameters, and B<SUB>i</SUB> is the local flux density in the sample. We also measured complex susceptibilities Xn=X′n-iX″n (n=1, 2, 3, 5, 7) of a melt-processed YBa<SUB>2</SUB>Cu<SUB>3</SUB>O<SUB>y</SUB> specimen and analyzed the observed Xn by applying the magnetization equations derived from the Kim-Anderson model. We found that the experimental results were qualitatively well reproduced. Present results indicate that, for a specimen of which J<SUB>c</SUB> sensitively varies with B<SUB>i</SUB>, the effect of a weak H<SUB>dc</SUB> should be explicitly taken into consideration for studies of the ac magnetization.
粉体および粉末冶金 45(7), 655-660, 1998-07-15
Japan Society of Powder and Powder Metallurgy