Magnetoresistance and anomalous thermal hysteresis in La_0.67Ca_0.33MnO₃/CaCu₃Ti₄O₁₂ composites

Abstract

The (1 − x) La0.67Ca0.33MnO3(LCMO)/xCaCu3Ti4O12 (CCTO) (x = 0, 0.01, 0.03, 0.05, and 0.10) composites were fabricated by the sol–gel method and investigated in detail for their electrical transport and magnetoresistance (MR) properties. The X‐ray diffraction and scanning electronic microscopy analysis reveal that both LCMO and CCTO phases are distributed in the composites. Compared with pure LCMO, an obvious enhancement of MR is observed over a wide temperature range for the composites at high external magnetic field. Under 3 T field, the MR increases to a maximum value of 73.4% for x = 0.1 composite. Simultaneously, the thermal hysteresis behavior in resistivity is observed in x = 0.03, 0.05, and 0.1 samples, respectively. The MR enhancement and the abnormal experimental observations are attributed to the enhanced spin disorder at grain boundaries induced by the interaction product layer between LCMO and CCTO.

Changes in the magnetization hysteresis direction and structure-driven magnetoresistance of a chalcopyrite-based magnetic semiconductor

“…Dho et al [2] reported an observation of the anomalous 'clockwise' behavior of a thermal hysteresis in magnetization and resistivity of half-doped manganites near the Néel temperature upon cooling and warming. Noteworthy is that the anomalous hysteresis characteristic in resistivity gives rise to a very large magnetoresistance (MR) effect [3,4]. Since the origin of such unusual behavior remains unclear, available reports explain it by the geometrical characteristics of the magnetic ordered interactions in the lattice [2] or enhanced spin disorder at grain boundaries [3,4].…”

“…Noteworthy is that the anomalous hysteresis characteristic in resistivity gives rise to a very large magnetoresistance (MR) effect [3,4]. Since the origin of such unusual behavior remains unclear, available reports explain it by the geometrical characteristics of the magnetic ordered interactions in the lattice [2] or enhanced spin disorder at grain boundaries [3,4]. Thus far, an anomalous change in hysteresis has been achieved by doping or applying a magnetic field.…”