INFRARED-ABSORPTION FROM CHARGE-DENSITY WAVES IN MAGNETIC MANGANITES

The infrared absorption of charge density waves coupled to a magnetic background is first observed in two manganites La1-xCaxMnO3 with x = 0 .5 and x = 0.67. In both cases a BCS-Like gap 2 Delta(T), which for x = 0.5 follows the hysteretic ferromagnetic-antiferromagnetic transitio n, fully opens at a finite T-0 < T-N, with 2 Delta(T-0)/k(B)T(c) simil ar or equal to 5. These results may also explain the unusual coexisten ce of charge ordering and ferromagnetism in La0.5Ca0.5MnO3. [S0031-900 7(98)07720-5].