Spin-Paramagnetic Transition

The data above shows the hystertic parallel critical field behavior of a 3.5 nm thick Al film at 60 mK. The hysteresis is seen in both transport and tunneling. The coherence length is ~15nm for the film in the figure, and the transition temperture was 2.7 K.

In the above plot we show the phase diagram for a thin Al film in parallel field. Note the tri-critical point at ~600 mK. N: normal state, S: superconducting phase, SM: state memory region. The latter is associated with the coexistance region of the intrinsically hysteretic first-order transition.