Elastic properties of giant magnetoresistive chalcogenides

We report on ultrasonic studies of the electron–lattice interaction in ferromagnetic lanthanum manganite and ferrimagnetic iron chrome sulfospinel which though adopting quite different crystal structures show giant magnetoresistive effects. Particular attention is paid here to the elastic behavior in the vicinity of the Curie temperature where the intrinsic magnetoresistances become largest. It is the main purpose of our investigations to draw attention to the important role of orbital degrees of freedom and their subtle interplay with the magnetic order parameter in these chalcogenides.