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要旨:
Using ac susceptibility, we have determined the pressure dependence of
the metamagnetic critical endpoint temperature T* for a field applied in
the ab plane in the itinerant metamagnet Sr3Ru2O7. We find that T* falls
monotonically to zero as pressure increases, producing a quantum
critical endpoint (QCEP) at P-c similar to 13.6 +/- 0.2 kbar. New
features are observed near the QCEP-the slope of T* versus pressure
changes at similar to 12.8 kbar, and weak subsidiary maxima appear on
either side of the main susceptibility peak at pressures near
P-c-indicating that some new physics comes into play near the QCEP.
Clear signatures of a nematic phase, however, that were seen in
field-angle tuning of T* are not observed. As T* is suppressed by
pressure, the metamagnetic peak in the susceptibility remains sharp as a
function of an applied magnetic field. As a function of temperature,
however, the peak becomes broad with only a very weak maximum,
suggesting that, near the QCEP, the uniform magnetization density is not
the order parameter for the metamagnetic transition.
