Alternating-field magnetoresistance measurements on Sr3Ru2O7

We apply an alternating-field (af) magnetoresistance technique to investigate the temperature-field (T-H) phase diagram of the bilayer ruthenate Sr3Ru2O7 in close vicinity of the metamagnetic quantum critical end point. The out-of-phase component of the af magnetoresistance is extremely sensitive to hysteresis effects. Clear peaks are observed when entering the bounded regime at low temperatures. They mark two separate first-order phase transitions ending at 0.7 and 0.45 K, respectively. No indication for hysteresis is observed inside the bounded regime. (C) 2007 Elsevier B.V. All rights reserved.