Erratum: Direct Observation of Ferromagnetic Spin Polarization in Gold Nanoparticles [Phys. Rev. Lett.93, 116801 (2004)]

Evidence of intrinsic magnetism in capped ZnO nanoparticles

“…The size and surface effects that modify the materials properties at nanoscale, provide a method to tune their physical properties opening the possibility to induce coexistence of properties not achievable at the bulk scale. [2][3][4] Actually, several recent reports claimed the observation of ferromagnetism in semiconductor and insulating oxide nanostructures without any doping despite the diamagnetic character of the material in bulk. [5][6][7][8] Among these, we recently reported the observation of room-temperature ferromagnetism of ZnO nanoparticles ͑NPs͒ capped with different molecules.…”

Giant magnetic anisotropy at the nanoscale: Overcoming the superparamagnetic limit

“…4,5 For the case of gold the appearance of magnetism was completely amazing provided the diamagnetic character of bulk samples and the low value of its density of states at the Fermi level. However, more unexpected was that NPs with sizes smaller than 2.4 nm could exhibit blocked magnetism at 300 K. [2][3][4][5] Moreover, the thermal dependence of magnetization for Pd and Au NPs is very weak between 5 and 300 K. By assuming a first order kinetics for the relaxation of the magnetic moments and an attempted frequency factor equal to approximately 10 10 s −1 , the anisotropy constant for a particle 2 nm size with blocking temperature above 300 K should be at least of10 9 J m −3 that corresponds to approximately 0.4 eV per atom. That is indeed an enormous value compared not only to the normal values for the harder magnetic materials but also to the value reported in Ref.…”

Oscillating spin-density pattern in gold metallocene and phthalocyanine molecules

“…Gold nanoparticles of diameters in the 2 nm range have been found recently to show room-temperature magnetism when capped with organic molecules. [1][2][3] Interestingly, the experiments have found that the magnetism of these nanoparticles is localized at their surface, where Au atoms are in chemical contact with the capping molecules. The different experiments produce different estimates for the spin moments M S of the surface gold atoms, which vary from 0.002 to 0.3 B , 3 but they agree on the very high value of the magnetic anisotropy energy ͑MAE͒, which is of about 0.4 eV/atom.…”

“…Fourth, we wish to understand better the magnetic properties of small gold molecules in view of the recent experiments mentioned above. [1][2][3] We find that the spin-density pattern of these molecules depends strongly on the identity of the M atom. We find that the atomic moments of cobalt molecules are strongly localized at the cobalt atom.…”

“…Huge orbital moments M L at the surface gold atoms have been proposed to exist and originate that large MAE, 4 but the actual measured moments seem to be modest, of order M L / M S ϳ 0.15. 1,3 Molecular magnets are in some ways superior to nanoparticles, since they have a well-defined number of atoms with precise chemical identities, and do not suffer from particle number dispersion. Further, molecules are not so prone to conformational changes, since these require breaking a sizable number of covalent bonds, as opposed to the metallic bonds of atomic clusters.…”