Angular dependence of the magnetic susceptibility in the itinerant metamagnet Sr₃Ru₂O₇

We report the results of a study of the differential magnetic susceptibility of Sr₃Ru₂O₇ as a function of temperature and magnetic fields applied at a series of angles to the ab plane. By analyzing the real and imaginary parts of the susceptibility, we conclude that the field angle acts as a continuous tuning parameter for the critical end point to a line of first-order metamagnetic phase transitions. The end point sits at approximate to1.25 K for fields applied in the ab plane, and is depressed to below 50 mK when the field is aligned within 10degrees of the c axis.