Effect of Magnetic Field Orientation on Thermal Conductivity in FeNi2 Alloys

Objectives: This study aims to quantify how the orientation of an external magnetic field influences the thermal conductivity of FeNi₂ (permalloy) alloys. Method: This study used a multiscale approach combining LAMMPS spin-lattice dynamics simulations and analytical calculations to investigate heat transport under different magnetic-field orientations. Findings: Simulations reveal a strong angular dependence in the thermal conductivity κ(θ). At 400 K, an enhancement of approximately 23% in thermal conductivity was observed when the heat flux is parallel to the magnetic field (θ = 0°); whereas, a reduction of nearly 19% occurs for the perpendicular configuration (θ = 90°). For (θ = 45°), the thermal conductivity remains nearly identical to that of the non-magnetic state. At this specific angle, the overall magnetothermal anisotropy is reduced due to a partial compensation between spin-dependent scattering mechanisms, which include spin-phonon interactions, magnon-related scattering, as well as spin-orbit coupling (SOC). Novelty: Unlike previous studies that mainly focused on the effect of magnetic-field intensity, this work demonstrates that the field orientation alone can be used to tune heat transport in FeNi₂ alloys. The identification of a characteristic angle at which the thermal conductivity approaches its non-magnetic value provides new insight into the directional control of thermal transport in ferromagnetic materials. Keywords: Thermal conduction, Magnetic field, Heat flux, FeNi2 alloys