期刊
JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS
卷 436, 期 -, 页码 77-84出版社
ELSEVIER SCIENCE BV
DOI: 10.1016/j.jmmm.2017.04.022
关键词
Double perovskite; Ac-susceptibility; Spin-glass; Memory effect; Exchange bias; Magnetoresistance
资金
- IIT Kharagpur through SGIRG challenge Grant Project [IIT/SRIC/PHY/UBF/2014-15/137]
Single-phase polycrystalline La1.5Ca0.5CoMnO6 double perovskite nanoparticles (similar to 25 nm) have been synthesized by chemical sol-gel method. We report here the structural, magnetic and transport properties using X-ray diffraction, dc magnetization, ac susceptibility, exchange bias and dc resistivity measurements. The Rietveld refinement of X-ray diffraction pattern reveals that the La1.5Ca0.5CoMnO6 (LCCMO) system crystallizes in orthorhombic structure with pbnm space group. Mn and Co ions are not completely ordered on the B sites due to the presence of about 30% antisite-disorder in the system. The ordering of Co2+ and Mn4+ gives rise to the ferromagnetism below 145 K. A spin glass like ground state has also been observed near 37.6(4) K, arising mainly due to the presence of competing magnetic interactions and antisite-disorder in the LCCMO nanoparticles. The frequency dependence peak shift of the Ac-susceptibility peak in the glassy state follows the critical slowing down model. The observed memory effect in ac susceptibility data reveals the existence of interacting clusters in a competing magnetic interactions state. The presence of noticeable exchange bias effect can be best explained on the basis of uncompensated interface (ferromagnetic/spin-glass) spins of antisite-disordered LCCMO system. This anti-site disordered nanocompound exhibits semiconducting behavior with variable range hopping kind of electronic conduction mechanism in the temperature range of 200-300 K. We have also observed large negative magnetoresistance (-30% at 100 K and 60 kOe) mainly due to the spin-polarized transport across the grain boundaries. (C) 2017 Elsevier B.V. All rights reserved.
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