MAGNETIC SHORT-RANGE ORDER EFFECTS IN THE 2D T-J MODEL

We outline an improved theory of short-range magnetic order for strong ly correlated itinerant electron systems, and apply it to the two-dime nsional t-J model. Within a spin-rotation-invariant slave-boson functi onal-integral scheme, the short-range order is incorporated at the sad dle-point and pair approximation levels. Comparing our numerical resul ts for the free energy with previous approaches, we observe that long- range-ordered antiferromagnetic and spiral phases are suppressed due t o the appearance of a paraphase with pronounced antiferromagnetic shor t-ranged correlations. In this phase, the presence of well-established local magnetizations is sufficient to describe the increase of the lo w-temperature susceptibility upon doping, which, e.g., is experimental ly observed for the high-T-c material La2-deltaSrdeltaCuO4. (C) 1998 E lsevier Science B.V. All rights reserved.