Orbital-dependent metamagnetic response in Sr4 Ru3 O10

We show that the metamagnetic transition in Sr4 Ru3 O10 bifurcates into two transitions as the field is rotated away from the conducting planes. This two-step process comprises partial or total alignment of moments in ferromagnetic bands followed by an itinerant metamagnetic transition whose critical field increases with rotation. Evidence for itinerant metamagnetism is provided by the Shubnikov-de Haas effect, which shows a nontrivial evolution of the geometry of the Fermi surface and an enhancement of the quasiparticles effective mass across the transition. We conclude that the metamagnetic response of Sr4 Ru3 O10 is orbital dependent and involves both ferromagnetic and metamagnetic bands.