Magnetization process in GdB4

Magnetization measurements are made on single crystal samples of GdB4 under static fields up to 14 T and pulsed fields up to similar to 60 T. When the external magnetic field, H, is applied along the [ 110] spin easy axis, the magnetization increases non-linearly at around 12T, indicating a spin reorientation from the easy axis to the direction perpendicular to H. The values of saturation field, H-s, are, H-s([110]) similar or equal to 52T, H-s([100]) similar or equal to 52T and H-s([001]) similar or equal to 54T. We analyze the results based on the two-dimensional model proposed by Shastry and Sutherland [B. S. Shastry and B. Sutherland: Physica B 108 (1981) 1069]. We obtain J(1)/k(B) = -8.9 K and J(2)/k(B) = -0.68 K, where, J(1) and J(2) are the diagonal exchange interaction and the exchange interaction along the edges of a square, respectively.