High-angle neutron diffraction was used to directly reveal the atomic-scale magnetic structure of a single-crystalline BiMn 0.5 Fe 0.5 O 3 thin film deposited on a SrTiO 3 (001) substrate. The BiMn 0.5 Fe 0.5 O 3 phase exhibits distinctive magnetic properties that differentiate it from both parent compounds: BiFeO 3 and BiMnO 3. A transition to long-range G-type antiferromagnetism was observed below 120 K with a (1 2 1 2 1 2) propagation vector. A weak ferromagnetic behavior was measured at low temperature by superconducting quantum interference device (SQUID) magnetometry. There is no indication of the spin cycloid, known for BiFeO 3, in the BiMn 0.5 Fe 0.5 O 3 thin film. The neutron diffraction suggests a random distribution of Mn and Fe over perovskite B sites. © 2012 American Institute of Physics.