Cyclotron spectrum analysis of ZTF J0112+5827. Top panel: Original spectra at phase 0.63 and phase 0.15 after removing emission lines and telluric features. Bottom panel: Difference spectrum (black line) was obtained by subtracting the phase 0.15 spectrum from the phase 0.63 spectrum, showing clear cyclotron harmonics. The best-fit theoretical cyclotron spectrum (red line) corresponds to a magnetic-field strength of $B=38.7_{-1.1}^{+1.3}$ MG and electron temperature of $T_e={37}_{-3}^{+2}$ keV.