Size-dependent magnetic moments in ultrafine diamagnetic systems

Abstract

Theory of magnetic fluid heating with an alternating magnetic field with temperature dependent materials properties for self-regulated heating Recently, unusual magnetic properties were found experimentally in otherwise diamagnetic nanoparticles. Our experiments and analysis revealed that a universal expression can describe the size-dependent magnetic moments in ultrafine diamagnetic systems, including Au, Pd, and HfO 2 nanoparticles. A model was presented to explain the observed phenomenon. It suggested that the up and down spins in ultrafine diamagnetic systems are spatially separated and form asymmetric spin-singlet pairs. The correlation lengths of the spin-singlet pairs in Au, Pd, and HfO 2 nanoparticles were estimated to be about 1.65, 13, and 4.4 nm, respectively. On the basis of this model, we explain (a) the origin and the size dependence of magnetic moments in diamagnetic nanoparticles, and (b) the origin of the extremely large anisotropy in diamagnetic nanoparticles.

Using Gradient Magnetic Fields to Control the Size and Uniformity of Iron Oxide Nanoparticles for Magnetic Resonance Imaging

“…Moreover, an external magnetic field can be conveniently applied to a reaction system. It is reported that the magnetic susceptibility of small nanoparticles changes rapidly with particle size. , Therefore, the applied external magnetic field will inevitably affect the motion of magnetic nanoparticles, whose size still changes during chemical synthesis. If the applied magnetic field changes, the force exerted by the field on each magnetic particle is proportional to the magnetic moment of the particle, which is related to its size.…”