Field induced two-dimensional ferromagnetic ordering in a gadolinium stearate Langmuir-Blodgett film

Abstract

Magnetic properties of materials confined to nanometer length scales are providing important information regarding low dimensional physics. Using gadolinium based Langmuir-Blodgett films, we have shown that a two-dimensional short range ferromagnetic order with no spontaneous magnetization occur as the field is applied along the normal to the growth (in-plane) direction. However, along the growth (out-of-plane) direction, we observe expected paramagnetic behavior down to a temperature of 2 K and a field of up to 70 kOe. We found that in-plane saturation moment increases and the field required to get this saturation decreases with decreasing temperature. These results are consistent with the theoretical predictions on isolated two-dimensional spin system having critical point at T=0. We have provided preliminary explanations of the observed field induced two-dimensional ferromagnetic ordering by considering asymmetric exchange coupling.