PARAMAGNETIC CONTRIBUTION TO THE REVERSIBLE MAGNETIZATION OF NB3PT

Reversible magnetization M(H,T) measurements are performed in a polycr ystalline bulk and powdered sample of Nb75Pt25. An essential suppressi on of the diamagnetic moment is found below a field H-p(T) < H-c2(T) f or the bulk sample, while for the powder it is not observed. This find ing, as well as the resistance R(H,T,J) behavior typical of Josephson junctions, and oscillations of M(H,T) just below a H-p-T-p line strong ly suggest a decisive role of the Josephson coupling (negative) in the occurrence of the paramagnetic contribution to the magnetization. The fully reversible magnetization excludes a trapped magnetic flux as an alternative explanation for the effect.