Magnetic phase transitions and bulk spin-valve effect tuned by in-plane field orientation in Ca₃Ru₂O₇

We have performed systematic in-plane angle-dependent c-axis transverse magnetotransport measurements on the double-layered ruthenate Ca ₃Ru₂O₇ throughout a broad field and temperature range. Our results reveal that the magnetic states unusually evolve with in-plane rotation of magnetic field. When magnetic field is applied along the b axis, we probe crossover magnetic states in close proximity to phase boundaries of long-range ordered antiferromagnetic states. These crossover magnetic states are characterized by short-range antiferromagnetic order and switch to polarized paramagnetic states at critical angles as the in-plane field is rotated from the b to the a axis. Additionally, we observe bulk spin-valve behavior resulting from spin-flop transitions tuned by in-plane rotation of magnetic field. Our results highlight the complex nature of the spin-charge coupling in Ca ₃Ru₂O₇ and posts a challenging question: why does the change of magnetic-field orientation result in magnetic phase transitions.