Tunable exchange bias, magnetoelectric transport and negative thermal expansion in Mn₃Ni_1-xCo_xN

Antiperovskite materials have significant potential in spintronics due to distinctive magnetic and electronic transport characteristics. This work systematically investigates the effects of Co substitution on the magnetic, electronic transport, and thermal expansion properties of Mn₃Ni_1-xCo_xN. Co substitution triggers a transformation from noncollinear antiferromagnetic to ferrimagnetic ordering. For x = 0.5, a pronounced exchange bias is observed, with a maximum exchange bias field of 7.44 kOe at 25 K and coercivity reaching 9.45 kOe at 75 K. This effect significantly modulates the anomalous Hall effect, providing clear evidence for spin-charge coupling in antiperovskites. All samples exhibit negative thermal expansion near magnetic transitions, with coefficients ranging from −65.64 × 10⁻⁶ K⁻¹ (x = 0) to −23.55 × 10⁻⁶ K⁻¹ (x = 0.7), revealing intrinsic correlations between magnetic transitions and lattice dynamics. This work advances the understanding of magnetic ordering mechanisms in antiperovskite materials and provides a basis for designing functional materials with tunable magnetic properties.