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Study of magnetic features of Nd₂Fe₁₄B through the spin reorientation transition by magnetic force microscopy Saleem, Muhammad
Nd₂Fe₁₄B is one of the high performance permanent magnets that has appeared as an appealing compound for commercial applications. The understanding of its macroscopic magnetic properties through the study of its magnetic domain structures has received great attention. In this study, we use magnetic force microscopy (MFM) to image the magnetic features as a function of temperature through the spin-reorientation transition temperature (TSR ∼ 135 K) of a Nd₂Fe₁₄B single crystal. We observe a pronounced change in the anisotropy of the magnetic features upon cooling from 170 K to 100 K. Our autocorrelation analysis of the MFM images reveals an increase in the four-fold component of the anisotropy below TSR. The magnetic feature size is estimated from the two-fold and four-fold components and found to be between 4.5 µm and 6 µm below TSR. We observe an average magnetic feature size around 5 µm above the spin reorientation transition. The complexity in the geometry of magnetic features is studied from the fractal dimension (FD) analysis. Higher values of FD below TSR indicate that the magnetic features possess more rugged boundaries. Average values of FD increase from 1.17 ± 0.05 for T > TSR to 1.29 ± 0.04 for T < TSR.
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