Magnetocaloric effect in Er- and Eu-substituted ferromagnetic La-Sr manganites

We have studied the magnetocaloric effect in La0.7Sr0.3MnO3 colossal magnetoresistive manganites, where La is substituted by Er or Eu. The addition of these rare-earth ions allows a tunable decrease in the Curie temperature, T-C. For example, in the LaEuSrMnO3 system T-C drops from 360 to 308 K for 0.14% of Eu substitution. We find quite large values of magnetic entropy change. For an applied magnetic field of 1 T, the maximum values for both studied systems are close to that of the parent La0.7Sr0.3MnO3, near their respective T-C's. Relative cooling power value increases notably for higher concentrations of Eu, in contrast to the Er-substituted samples. These results are discussed in terms of magnetoelastic and electron interaction contribution to the magnetic entropy. (c) 2004 Elsevier B.V. All rights reserved.