Metamagnetism inLa2CuO4

A careful study of the metamagnetic transition in single-crystalline ${\mathrm{La}}_2$ ${\mathrm{CuO}}_4$ is presented. From magnetic susceptibility measurements the critical exponent (β) of the weak ferromagnetic state, which terminates at a triple point, has been estimated to be β=0.5±0.02, a value consistent with mean-field theory. Furthermore, the pressure dependence of the critical magnetic field for the transition has been examined from magnetoresistance measurements under hydrostatic pressure.