Coupled magnetic and electric hysteresis in the multiferroic double perovskite Lu2MnCoO6

We investigate a magnetic hysteresis loop with a remanent moment that couples to electric polarization to create coupled hysteretic multiferroic behavior in Lu2MnCoO6. Measurements of elastic neutron diffraction, muon spin relaxation, and micro-Hall magnetometry demonstrate an unusual mechanism for the magnetic hysteresis, namely the hysteretic evolution of a microscopic magnetic order, and not classic ferromagnetic domain effects. We show how the frustrated spin system evolves from antiferromagnetism with an incommensurate long-wavelength modulation and strong fluctuations towards a net magnetism. We also clarify the different temperature scales for the onset of ordering, dynamics, and hysteresis.