Inverted hysteresis and negative remanence in a homogeneous antiferromagnet

Magnetic remanence—found in bar magnets or magnetic storage devices—is probably the oldest and most ubiquitous phenomenon underpinning the technological applications of magnetism. It is a macroscopic nonequilibrium phenomenon: A remanent magnetization appears when a magnetic field is applied to an initially unmagnetized ferromagnet, and then taken away. Here, we present an inverted magnetic hysteresis loop in the pyrochlore compound Nd₂Hf₂O₇: The remanent magnetization points in a direction opposite to the applied field. This phenomenon is exquisitely tunable as a function of the protocol in field and temperature, and it is reproducible as in a quasiequilibrium setting.