Exchange-narrowing spin-spin interaction in the paramagnetic regime of perovskite manganites studied through the EPR measurements for (La, Y)(2/3)(Ca, Sr, Ba)(1/3)MnO3 with a wide span of T-c

The electron paramagnetic resonance (EPR) spectrum as a function of T is ex perimentally studied for (La, Y)(2/3)(Ca, Sr, Ba)(1/3)MnO3 with a wide span of T-C. In the real paramagnetic regime (T greater than or equal to T-min) , the spectrum consists of a single line with the resonance held being inde pendent of T. The resonance linewidth is given by Delta H-pp = Delta H-pp,H -min + b(T - T-min). The exchange-narrowing spin-spin interaction and the s pin-lattice interaction are explained to be responsible for the terms of De lta H-pp,H-min and b(T - T-min), respectively. Based on the exchange narrow ing mechanism, the values of Delta H-pp,H-min are directly deduced from the T-C-values, which are well consistent with the experimental Delta H-pp,H-m in-values. This confirms the possibility that the exchange-narrowing spin-s pin interaction exists in the ABO(3)-type perovskite manganites.