Influence of magnetic frustration and structural disorder on magnetocaloric effect and magneto-transport properties in La_(1.5)Ca_(0.5)CoMnO_6 double perovskite

摘要

The rare existence of a magnetocaloric effect, a Griffith phase, and frustrated magnetism in the antisite disorder compound La_(1.5)Ca_(0.5)CoMnO_6 have been investigated in detail in this work. The nature of the observed Griffith phase (at T_G～226 K) can be best understood in terms of ferromagnetic (FM) entities within the globally paramagnetic network above the Curie temperature. From the isothermal magnetization measurement around Curie temperature (T_C～157 K) and cluster glass transition temperature (T_g～51 K), we have determined the maximum entropy change (-ΔS_M) as ～2.2 J/kg K and ～1.2 J/kg K, respectively, for a magnetic field variation of 7T. Interestingly, a sudden drop of resistivity curve at T_g, associated with magnetic frustration or magnetic disorder, can be related to the ferromagnetic (FM) phases with antiferromagnetic antiphase boundaries, giving rise to a large negative magnetoresistance (～67%) at 45 K.