Fig. 4: Relations between dipole fields and microstructures.
a Schematic of the two-grain model, wherein hexagonal flat grains are stacked along the z-direction. b Calculated dipole field along the z-direction at an interface between two grains. c Dipole field as a function of the easy-axis tilt angles of upper (Δθ1) and lower grains (Δθ2). The dipole field along the z-direction is indicated by different colors. White colors represent contour lines. d Easy-axis tilt angle of a grain (Δθi). Δθi,1, Δθi,2, and Δθi,3 are the first-, second-, and third-largest easy-axis tilt angles among those of the contacted grains along the z-direction, respectively. Gray regions and red arrows represent the grains and the easy-axis orientations, respectively. e Relationship between the maximum dipole field along the z-direction and Δθi + Δθi,1. Colors represent the grain coercivity calculated using Eq. 5. The dotted line represents the relationship between the dipole field of the two-grain model and the tilted angles of the grains. Grains demonstrating regions of magnetization reversal in Fig. 2d are indicated by arrows. f Dipole field along the z-direction near grains A and B indicated in e.
