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The magnetic susceptibility of the two-dimensional repulsive Hubbard modelwith nearest-neighbor hopping is investigated using the diagram techniquedeveloped for the case of strong correlations. In this technique a power seriesin the hopping constant is used. At half-filling the calculated zero-frequencysusceptibility and the square of the site spin reproduce adequately results ofMonte Carlo simulations. Also in agreement with numerical simulations noevidence of ferromagnetic correlations was found in the considered range ofelectron concentrations $0.8\alt\bar{n}\alt 1.2$ for the repulsion parameters$8|t|\leq U\leq 16|t|$. However, for larger $U/|t|$ and $|1-\bar{n}|\approx0.2$ the nearest neighbor correlations become ferromagnetic. For $\bar{n}\alt0.94$ and $\bar{n}\agt 1.06$ the imaginary part of the real-frequencysusceptibility becomes incommensurate for small frequencies. Theincommensurability parameter grows with departure from half-filling anddecreases with increasing the frequency. This behavior of the susceptibilitycan explain the observed low-frequency incommensurate response observed innormal-state lanthanum cuprates.

Magnetic susceptibility of the two-dimensional Hubbard model using a power series for the hopping constant