CORRELATION BETWEEN STRUCTURAL TRANSFORMATION AND SUPERCONDUCTIVITY IN B2 ALLOYS V-RU-OS

The inter-relationship, between structural transformation and superconductivity has been studied on B2 systems: 1) V//5//4// minus //xRu//4//6Os//x, 2) V//5//4Ru//4//6// minus //xOs//x and 3) V//5//2Ru//4//8// minus //xOs//x with 0 less than equivalent to x less than equivalent to 4. An increase of the parameter x in where the electron-atom ratio e/a increases linearly with x, raises the transformation temperature T//L sharply while lowering the superconducting transition temperature T//c rapidly. This is in contrast with the results for both systems 2) where e/a is a constant independent of x. All samples in 2) with e/a equals 6. 38 undergo no structural transformation, while showing superconductivity at nearly the same temperatures around 5 K. All samples in 3) with e/a equals 6. 44, however, show no superconductivity, while undergoing transformation at nearly the same temperatures around 200 K. Taken together, these facts confirm that both T//L and T//c are completely dominated by the value of e/a; the lowering of T//L, which is accompanied by a decrease of e/a, causes sharp enhancement of T//c. This provides decisive evidence for the electronic transition and its strong correlation with superconductivity.