MAGNETIC TRANSITION IN La2CuO4 INDUCED BY MAGNETIC FIELD PARALLEL TO CuO2 PLANE
La2CuO4在平行CuO2面磁场中的磁转变

In this letter, we develop a theory in the mean-field approximation for the spin-flop transition in La2CuO4 when the magnetic field is parallel to the CuO2 plane. The temperature dependence of the critical field predicted by our theory agree qualitatively with the experiment. However, there is no multicritical point according to our theory. The origin of this disagreement is discussed briefly.