ANALYSIS OF TEMPERATURE TRANSFORMATION OF MAGNETIC DOMAIN STRUCTURE OF Nd2Fe14B SINGLE CRYSTAL IN THE MODEL OF FRACTAL THERMODYNAMICS

The fractal thermodynamics model was applied for the first time to study the process of temperature-induced transformation of the magnetic domain structure (DS) on the basal plane of an Nd₂Fe₁₄B single crystal within the temperature range of 20–285 K. This range encompasses a second-order spin-reorientation transition (SRT) from the “easy axis” type of magnetocrystalline anisotropy (MCA) to the “easy cone” type of MCA. A high degree of similarity between the patterns of the Nd₂Fe₁₄B single crystal's domain structure images and fractals was demonstrated across the entire temperature interval. Specifically, the values of the parameter δ, characterizing the relative deviation of the studied DS from fractals, fall within the range of 1.16⋅10⁻⁶ to 1.72⋅10⁻². A notable difference was observed in the character of the temperature dependencies of the fractal parameters D(T), S_f(T), and T_f(T) at temperatures below and above the SRT temperature T_SRT = 135 K. Furthermore, the temperature behavior of the fundamental constants of the Nd₂Fe₁₄B compound and the fractal parameters of the DS within the “easy axis” MCA region suggests a possible correlation between them in this temperature range.