Resistance hysteresis in paramagnetic tungsten nitride (W₅N₆)

Two-dimensional (2D) transition metal nitrides (TMNs), which are members of the family of 2D materials, may find practical applications in electronics and optoelectronics because of their superior physical properties. Recently, wafer-scale, single-unit-cell height P62m W₅N₆, which was difficult to be synthesized in the past, has been grown using a restricted vapor-liquid-solid method. Here, we report experimental evidence for hysteretic magnetoresistance (MR) mediated by temperature in paramagnetic W₅N₆. Surprisingly, hysteretic MR is weak or even non-existent at millikelvin temperatures where hysteresis is expected to be most pronounced. With increasing temperature, hysteretic behavior becomes the strongest at around 9 K. With further increase in temperature, hysteresis becomes weaker and undetectable at around 26 K. The observed paramagnetism in the Efros-Shklovskii variable range hopping (E-S VRH) regime, where Coulomb interactions are important, provides a paradigm for probing magnetism in 2D TMNs. Importantly, such paramagnetism in TMNs in the E-S VRH regime, which is supported by density functional theory calculations, may find applications in medical imaging, magnetic refrigeration, and magnetic sensing.