Magnetic characteristics of copper ion-modified dna thin films

We developed a new method of fabricating a divalent copper ion (Cu ²⁺) modified DNA thin film on a glass substrate and studied its magnetic properties. We evaluated the coercive field (H c), remanent magnetization (M r), susceptibility (χ), and thermal variation of magnetization with varying Cu²⁺ concentrations [Cu²⁺[ resulting in DNA thin films. Although thickness of the two dimensional DNA thin film with Cu²⁺ in dry state was extremely thin (0.6 nm), significant ferromagnetic signals were observed at room temperature. The DNA thin films with a [Cu²⁺[ near 5 mM showed the distinct S-shape hysteresis with appreciable high H c, M r and χ at low field (≤600 Oe). These were primarily caused by the presence of small magnetic dipoles of Cu²⁺ coordination on the DNA molecule, through unpaired d electrons interacting with their nearest neighbors and the inter-exchange energy in the magnetic dipoles making other neighboring dipoles oriented in the same direction.