Phase Diagram of the First-Order Vortex-Core Transition in Superfluid 3He-B

The phase diagram of quantized vortices in ³He-B has been obtained with two techniques. Our NMR measurements show that magnetization displays a pressure-dependent first-order phase change at T_V(P). Our gyroscopic experiments reveal a transition curve T_G(P) which marks an abrupt change in the critical velocity. Both curves show a weak magnetic field dependence, run similarly in the (P, T) plane, and seem to mark the same vortex-core transition.