Low-temperature Ferromagnetism in a Weakly Doped Hubbard Magnet

• Main Author: Zubov, E.E.
• Format: Article
• Language: English
• Published: Відділення фізики і астрономії НАН України 2010
• Series: Український фізичний журнал
• Subjects: Тверде тіло
• Online Access: http://dspace.nbuv.gov.ua/handle/123456789/56195

In the framework of the diagrammatic method with self-consistent field, the maximum on the temperature dependence of the susceptibility of a weakly doped narrow-band Hubbard magnet below the Curie temperature TC is predicted. By numerical calculations, it is proved that it appears at small hole concentrations nh. In this case, the temperature dependence of the magnetization M(T) has a typical Fermi-like shape with the point of inflection at a temperature Tinf . The approximate solution of the system of equations for the mean spin and the chemical potential gives the Schottky susceptibility typical of a two-level system with a gap of order of nh(1 - nh)W, where W is the bandwidth. This behavior reflects the existence of two subbands with up- and down-spins. It may be observed experimentally in the surface layers of oxide metal nanoparticles with narrow bands and a weak oxygen nonstoichiometry.