Observation of the pressure-induced weak ferromagnetic moment in the layered antiferromagnetic compound (C2H5NH3)2CuCl4 by magnetic susceptibility and neutron scattering measurements

In the two-dimensional Heisenberg antiferromagnet (C2H5NH3)(2)CuCl4, the intralayer exchange interaction is ferromagnetic, whereas the interlayer exchange interaction, which is less than 10(-4) of the intralayer one; is antiferromagnetic, and the spins collinearly lie in each layer. To investigate the effect of pressure on its spin structure, magnetic susceptibility and neutron scattering measurements under pressures up to 2.5 GPa were performed. The magnetic susceptibility measurements revealed the appearance of a pressure-induced weak ferromagnetic moment along the c-axis around 0.6GPa. The neutron scattering measurements clarified the noncollinear spin structure which causes the weak ferromagnetic moment mentioned above. That is, the fer romagnetically coupled spins in each layer cant from the layer, which brings about the weak ferromagnetic moment along the c-axis. The ferromagnetic coupling in each layer and the antiferromagnetic coupling among the nearest-neighboring layers are maintained at least; up to 2.5 GPa.