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Abstract:
We present measurements on ultraclean single crystals of the bilayered
ruthenate metal Sr3Ru2O7, which has a magnetic-field-tuned quantum
critical point. Quantum oscillations of differing frequencies can be
seen in the resistivity both below and above its metamagnetic
transition. This frequency shift corresponds to a small change in the
Fermi surface volume that is qualitatively consistent with the small
moment change in the magnetization across the metamagnetic transition.
Very near the metamagnetic field, unusual behavior is seen. There is a
strong enhancement of the resistivity in a narrow field window, with a
minimum in the resistivity as a function of temperature below 1 K that
becomes more pronounced as the disorder level decreases. The region of
anomalous behavior is bounded at low temperatures by two first-order
phase transitions. The implications of the results are discussed.
