Inverted hysteresis loops (IHLs) exhibiting negative coercivity and remanence represent a counterintuitive phenomenon in magnetic systems, with origins remaining elusive. Here, we address this long-standing paradox through combined experimental and theoretical investigations of two prototypical heterostructures: a metallic exchange-spring system (NiFe/CoFeB/MgO) and a hybrid ferromagnetic semiconductor-topological insulator ($\mathrm{M}{\mathrm{n}}_x\mathrm{G}{\mathrm{e}}_{1-x}/\mathrm{B}{\mathrm{i}}_2\mathrm{S}{\mathrm{e}}_3$). In the former, complete IHLs occur under out-of-plane fields, accompanied by unprecedented asymmetric angular dependence of remanence, a hallmark of noncollinear magnetic configurations. Our minimal bilayer model reveals that such anomalous hysteresis universally originates from the interfacial nonlinear spin configurations induced by the synergistic effect of inhomogeneous magnetic parameters and antiferromagnetic exchange coupling, where IHL becomes energetically stabilized only when the interlayer coupling strength exceeds a critical threshold. Guided by this principle, we engineered the latter system, where $\mathrm{B}{\mathrm{i}}_2\mathrm{S}{\mathrm{e}}_3$'s spin texture couples antiferromagnetically with $\mathrm{M}{\mathrm{n}}_x\mathrm{G}{\mathrm{e}}_{1-x}$'s magnetization, observing temperature-robust IHLs from 10 K to 250 K. Crucially, energy analysis demonstrates that the apparent “negative coercivity” corresponds to a metastable minimum in the free-energy landscape, reconciling IHLs with fundamental thermodynamic laws. This work establishes interfacial coupling as a universal design rule for manipulating hysteresis topology, offering direct implications for spin-orbit torque devices and topological spintronic applications.

Close

PrevNext

View figure in article

• Magnetic coupling
• Bilayer films
• Ferromagnets
• Heterostructures
• Magnetization measurements