Universal distribution of magnetic anisotropy of impurities in ordered and disordered nanograins
2015 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 91, no 13, 134421Article in journal (Refereed) Published
We examine the distribution of the magnetic anisotropy experienced by a magnetic impurity embedded in a metallic nanograin. As an example of a generic magnetic impurity with a partially filled d shell, we study the case of d(1) impurities embedded into ordered and disordered Au nanograins, described in terms of a realistic band structure. Confinement of the electrons induces a magnetic anisotropy that is large, and can be characterized by five real parameters, coupling to the quadrupolar moments of the spin. In ordered (spherical) nanograins, these parameters exhibit symmetrical structures and reflect the symmetry of the underlying lattice, while for disordered grains they are randomly distributed and, for stronger disorder, their distribution is found to be characterized by random matrix theory. As a result, the probability of having small magnetic anisotropies K-L is suppressed below a characteristic scale Delta(E), which we predict to scale with the number of atoms N as Delta(E) similar to 1/N-3/2. This gives rise to anomalies in the specific heat and the susceptibility at temperatures T similar to Delta(E) and produces distinct structures in the magnetic excitation spectrum of the clusters that should be possible to detect experimentally.
Place, publisher, year, edition, pages
2015. Vol. 91, no 13, 134421
IdentifiersURN: urn:nbn:se:uu:diva-253051DOI: 10.1103/PhysRevB.91.134421ISI: 000353122600003OAI: oai:DiVA.org:uu-253051DiVA: diva2:820724