A magnetostructural phase transition is investigated in single-crystal chromium nitride (CrN) thin films grown by rf plasma molecular beam epitaxy on MgO(001) substrates. While still within the vacuum environment following molecular beam epitaxy growth, in situ low-temperature scanning tunneling microscopy, and in situ variable low-temperature reflection high-energy electron diffraction are applied, revealing an atomically smooth and metallic CrN(001) surface, and an in-plane structural transition from $1\times 1$ (primitive CrN unit cell) to $\sqrt{2}\times \sqrt{2}-R{45}^{\circ }$ with a transition temperature of ($278\pm 3$) K, respectively. Ex situ temperature-dependent measurements using neutron diffraction are also performed, looking at the structural peaks and likewise revealing a first-order structural transition along the [111] out-of-plane direction, with transition temperatures of (268 $\pm$ 3) K. Turning to the magnetic peaks, neutron diffraction confirms a clear magnetic transition from paramagnetic at room temperature to antiferromagnetic at low temperatures with a sharp, first-order phase transition and a Néel temperature of ($270\pm 2$) K or ($280\pm 2$) K for two different films. In addition to the experimental measurements of structural and magnetic ordering, we also discuss results from first-principles theoretical calculations which explore various possible magnetostructural models.

The nanohybrid development of metal oxide/conducting polymer as an energy storage material is an active research area, because of the device stability, conductive behavior, and easy fabrication. Herein, needle-like MnO₂ was coupled with polyaniline fabricated through chemical polymerization followed by the hydrothermal process. The characterization results show that MnO₂/polyaniline exhibited a needle-like morphology. Different characterization techniques such as X-ray diffraction patterns and scanning electron microscopy confirmed the formation of the MnO₂/polyaniline nanohybrids. The electrochemical performance, including cyclic voltammetry (CV), galvanostatic charge–discharge (GCD), specific capacitance (C_sp), and cyclic stability, was examined using a three-electrode assembly cell. The optimized electrode displayed a C_sp of 522.20 F g⁻¹ at a current load of 1.0 A g⁻¹ compared with the other electrodes. The developed synergism during MnO₂/polyaniline fabrication provided enhanced conductive channels and stability during the charge–discharge process.