Magnetic nanoparticles

Intrinsic properties of magnetic nanoparticles are reviewed, with special emphasis on the effects of finite size on zero-temperature spin ordering, magnetic excitations, and relaxation. Effects on zero-temperature spin ordering include moment enhancement due to band narrowing in 3d transition metal particles, surface spin disorder in ferrite particles, and multi-sublattice states in antiferromagnetic oxide particles. Magnetic excitations include discretized spin wave modes, and surface modes that have been detected by quasielastic neutron scattering. Thermally activated and quantum tunneling relaxation is discussed in the context of ideal single-domain particles, as well as particles with surface spin disorder.