Magnetic entropy change and colossal magnetoresistance effect in the layered perovskite La1.34Sr1.66Mn2O7

Magnetocaloric and electronic properties of the layered perovskite La1.34Sr1.66Mn2O7 manganese oxide have been investigated. Broadening of the magnetic entropy change peak was observed above Curie temperature (Tc=118 K), which can be associated with the existence of two-dimensional short-range magnetic order in the bilayered perovskite. There is an additional reinforcement of the magnetization in a narrow range under Tc when magnetic field is above ∼2 T, leading to a positive magnetic entropy change. It is noticeable that a wide peak of magnetoresistance (MR ∼66%) near Tc as well as two field-dependent peaks in R–T curves was found in our sample.