Low-temperature thermodynamics of magnetically ordered states of a narrow-band Hubbard magnet

The effect of exchange and doping on the structure of the ground state of a narrow-band Hubbard magnet is investigated by using the t-J model. The boundaries of ferro–, antiferro–, and paramagnetic phases are determined. The low-temperature thermodynamics of the ferromagnetic state is studied. It is found that thermal fluctuations affect the saturated ferromagnetic state and cause a concentration drop of magnetization to zero at temperatures T/W ≪ 1 (W is the band width). The experimentally observed peculiarities in the behavior of susceptibility, such as a paramagnetic increase in proportion to 1/T and the emergence of a Schottky-type peak, are explained qualitatively.

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