EPR AND AFMR OF LI2CUO2 IN SUBMILLIMETER WAVE REGION

Paramagnetic and antiferromagnetic resonances have been observed for powder samples of Li2CuO2 in submillimeter wave region using pulsed magnetic fields at temperatures from 1.9 K to 265 K. At the paramagnetic state, the g-values have been determined to be g(parallel-to) = 2.30 and g(perpendicular-to) = 2.01. The line-width estimated from the powder signal increases as the frequency increases. Antiferromagnetic resonance modes along the principal axes have been clearly observed even in the powder samples below the Neel temperature and explained by the conventional antiferromagnetic resonance theory. It has been found that the easy axis is parallel to the direction of g(parallel-to) and the anisotropy is almost uniaxial and fairly strong. This fact is quite different from other antiferromagnetic copper oxides. Obtained parameters by AFMR are A = 90 mol/emu, A(x)'= 0.061 A, A(y)' = -0.021 A, A(z)' = -0.040 A, GAMMA(x)' = -0.028 A, GAMMA(y)' = 0.018 A and GAMMA(z)' = 0.010 A.