Figure 3. Magnetic characteristics of the copper ion modified DNA thin films.

(a) The variation of coercive field (H_c) and remanent magnetization (M_r) without and with various [Cu²⁺]. (b) Variation of susceptibility (χ) at 600 Oe for Cu²⁺ alone and various [Cu²⁺] used in forming the DNA thin films. Inset shows the average χ. (c, d) Temperature dependence of magnetization (M-T) and inverse χ (χ⁻¹ − T) for various [Cu²⁺] DNA complexes. From M-T, the nonzero magnetization can be observed and is roughly constant between 20 and 300 K with no indication of a magnetic transition up to 300 K.