Giant spontaneous exchange bias in an antiperovskite structure driven by a canted triangular magnetic structure
Exchange bias (EB) effect, generally observed in systems consisting of ferromagnetic and antiferromagnetic layers after a cooling procedure in a high magnetic field, is highly desirable for technological applications ranging from spintronics to magnetic recording. Achieving a giant EB effect near room temperature in a small cooling field is thus an on-going technologically relevant challenge for the materials science community. In this work, we present the experimental realization of such a fundamental goal by demonstrating the existence of giant EB after a zero field cooled (ZFC) procedure in antiperovskite Mn3.5Co0.5N below 256 K. We found that it exhibits an EB field of −0.28 T at 50 K after a ZFC procedure accompanied by a large vertical magnetization shift (VMS). Interestingly, this EB field can be elevated up to −1.2 T after a cooling procedure with a small applied field of just 500 Oe. Mn3.5Co0.5N represents the first intermetallic material showing a strong correlation between EB and VMS. We attribute the observed EB effect to a new canted triangular magnetic structure in antiperovskites determined by a neutron diffraction experiment. Finally, we discuss the striking effect of Co substitution on the physical properties of antiperovskite materials and put forward a new strategy for the antiperovskite lattice to exploit new single phase materials showing large EB effect at room temperature.