Magnetic Excitations of the 2-D Sm Spin Layers in Sm(La,Sr)CuO4
  We present specific heat and susceptibility data on Sm(La,Sr)CuO4 in magnetic fields up to 9 T and temperatures down to 100 mK. We find a broad peak in specific heat which is insensitive to magnetic field at a temperature of 1.5 K with a value of 2.65 J/mol K. The magnetic susceptibility at 5 T continues to increase down to 2 K, the lowest temperature measured. The data suggest that the Sm spin system may be an ideal realization of the frustrated Heisenberg antiferromagnet on the square lattice. 
F. Ronning, C. Capan, N.O. Moreno, J.D. Thompson, L.N. Bulaevskii, R.   Movshovich, D. van der Marel